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  • CRISPR-Cas9 assisted functional gene editing in the mushroom Ganoderma lucidum
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-21
    Ping-An Wang, Han Xiao, Jian-Jiang Zhong

    Abstract The genetic manipulation of basidiomycete mushrooms is notoriously difficult and immature, and there is a lack of research reports on clustered regularly interspaced short palindromic repeat (CRISPR) based gene editing of functional genes in mushrooms. In this work, Ganoderma lucidum, a famous traditional medicinal basidiomycete mushroom, which produces a type of unique triterpenoid-anti-tumor ganoderic acids (GAs), was used, and a CRISPR/CRISPR-associated protein-9 nuclease (Cas9) editing system for functional genes of GA biosynthesis was constructed in the mushroom. As proof of concept, the effect of different gRNA constructs with endogenous u6 promoter and self-cleaving ribozyme HDV on ura3 disruption efficiency was investigated at first. The established system was applied to edit a cytochrome P450 monooxygenase (CYP450) gene cyp5150l8, which is responsible for a three-step biotransformation of lanosterol at C-26 to ganoderic acid 3-hydroxy-lanosta-8, 24-dien-26 oic acid. As a result, precisely edited cyp5150l8 disruptants were obtained after sequencing confirmation. The fermentation products of the wild type (WT) and cyp5150l8 disruptant were analyzed, and a significant decrease in the titer of four identified GAs was found in the mutant compared to WT. Another CYP gene involved in the biosynthesis of squalene-type triterpenoid 2, 3; 22, 23-squalene dioxide, cyp505d13, was also disrupted using the established CRISPR-Cas9 based gene editing platform of G. lucidum. The work will be helpful to strain molecular breeding and biotechnological applications of G. lucidum and other basidiomycete mushrooms.

    更新日期:2020-01-27
  • Characterization of an 17β-estradiol-degrading bacterium Stenotrophomonas maltophilia SJTL3 tolerant to adverse environmental factors
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-13
    Weiliang Xiong, Chong Yin, Wanli Peng, Zixin Deng, Shuangjun Lin, Rubing Liang

    Abstract Bioremediation of environmental estrogens requires microorganisms with stable degradation efficiency and great stress tolerance in complex environments. In this work, Stenotrophomonas maltophilia SJTL3 isolated from wastewater was found to be able to degrade over 90% of 10 μg/mL 17β-estradiol (E2) in a week and the degradation dynamic was fitted by the first-order kinetic equations. Estrone was the first and major intermediate of E2 biodegradation. Strain SJTL3 exhibited strong tolerance to several adverse conditions like extreme pH (3.0–11.0), high osmolality (2%), co-existing heavy metals (6.25 μg/mL of Cu2+) and surfactants (5 CMC of Tween 80), and retained normal cell vitality and stable E2-degradaing efficiency. In solid soil, strain SJTL3 could remove nearly 100% of 1 μg/mL of E2 after the bacteria inoculation and 8-day culture. As to the contamination of 10 μg/mL E2 in soil, the biodegradation efficiency was about 90%. The further obtainment of the whole genome of strain SJTL3 and genome analysis revealed that this strain contained not only the potential genes responsible for estrogen degradation, but also the genes encoding proteins involved in stress tolerance. This work could promote the estrogen-biodegrading mechanism study and provide insights into the bioremediation application.

    更新日期:2020-01-15
  • Fungal P 450 monooxygenases - the diversity in catalysis and their promising roles in biocontrol activity
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-19
    Razak Hussain, Mushtaq Ahmed, Tabreiz Ahmad Khan, Yusuf Akhter

    Abstract The fungal P450s catalyze vital monooxygenation reactions in primary and secondary metabolism, which may lead to the production of diverse secondary metabolites. Many of these, such as from the family of trichothecenes, involve in biocontrol activities. The diversified nature of fungal P450 monooxygenases makes their host organisms adoptable to various ecological niches. The available genome data analysis provided an insight into the activity and mechanisms of the fungal P450s. However, still more structural and functional studies are needed to elucidate the details of its catalytic mechanism, and the advance studies are also required to decipher further about their dynamic role in various aspects of trichothecene oxygenations. This mini review will provide updated information on different fungal P450 monooxygenases, their genetic diversity, and their role in catalyzing various biochemical reactions leading to the production of plant growth promoting secondary metabolites.

    更新日期:2020-01-15
  • Engineered bacterial biofloc formation enhancing phenol removal and cell tolerance
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-13
    Xiao Jia, Shun Zhang, Jiawei Li, Juan Xia, Ruilian Yao, Xinqing Zhao, Bing Wu, Fengwu Bai, Yi Xiao

    Abstract A microbial floc consisting of a community of microbes embedded in extracellular polymeric substances matrix can provide microbial resistances to toxic chemicals and harsh environments. Phenol is a toxic environmental pollutant and a typical lignin-derived phenolic inhibitor. In this study, we genetically engineered Escherichia coli cells by expressions of diguanylate cyclases (DGCs) to promote proteinaceous and aliphatic biofloc formation. Compared with the planktonic E. coli cells, the biofloc-forming cells improved phenol removal rate by up to 2.2-folds, due to their substantially improved tolerance (up to 149%) to phenol and slightly enhanced cellular activity (20%) of phenol hydroxylase (PheH). The engineered bioflocs also improved E. coli tolerance to other toxic compounds such as furfural, 5-hydroxymethylfurfural, and guaiacol. Additionally, the strategy of the engineered biofloc formation was applicable to Pseudomonas putida and enhanced its tolerance to phenol. This study highlights a strategy to form engineered bioflocs for improved cell tolerance and removal of toxic compounds, enabling their universality of use in bioproduction and bioremediation.

    更新日期:2020-01-15
  • Diversity of volatile organic compound production from leucine and citrate in Enterococcus faecium
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-11
    Matilde D’Angelo, Gabriela P. Martino, Victor S. Blancato, Martín Espariz, Axel Hartke, Nicolas Sauvageot, Abdellah Benachour, Sergio H. Alarcón, Christian Magni

    Abstract Enterococcus faecium is frequently isolated from fermented food; in particular, they positively contribute to the aroma compound generation in traditional cheese. Citrate fermentation is a desirable property in these bacteria, but this feature is not uniformly distributed among E. faecium strains. In the present study, three selected E. faecium strains, IQ110 (cit−), GM70 (cit+ type I), and Com12 (cit+ type II), were analyzed in their production of aroma compounds in milk. End products and volatile organic compounds (VOCs) were determined by solid-phase micro-extraction combined with gas chromatography mass spectrometry (SPME-GC-MS). Principal component analysis (PCA) of aroma compound profiles revealed a different VOC composition for the three strains. In addition, resting cell experiments of E. faecium performed in the presence of leucine, citrate, or pyruvate as aroma compound precursors allowed us to determine metabolic differences between the studied strains. GM70 (cit+ type I) showed an active citrate metabolism, with increased levels of diacetyl and acetoin generation relative to Com12 or to citrate defective IQ110 strains. In addition, in the experimental conditions tested, a defective citrate-fermenting phenotype for the Com12 strain was found, while its leucine degradation and pyruvate metabolism were conserved. In conclusion, rational selection of E. faecium strains could be performed based on genotypic and phenotypic analyses. This would result in a performing strain, such as GM70, that could positively contribute to flavor, with typical notes of diacetyl, acetoin, 3-methyl butanal, and 3-methyl butanol in an adjuvant culture.

    更新日期:2020-01-15
  • Zinc supplementation improves the harvest purity of β-glucuronidase from CHO cell culture by suppressing apoptosis
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-19
    Ryan J. Graham, Stephanie Ketcham, Adil Mohammad, Bandaranayake M. B. Bandaranayake, Ty Cao, Bidesh Ghosh, James Weaver, Seongkyu Yoon, Patrick J. Faustino, Muhammad Ashraf, Celia N. Cruz, Chikkathur N. Madhavarao

    The variability of trace metals in cell culture media is a potential manufacturing concern because it may significantly affect the production and quality of therapeutic proteins. Variability in trace metals in CHO cell culture has been shown to impact critical production metrics such as cell growth, viability, nutrient consumption, and production of recombinant proteins. To better understand the influence of excess supplementation, zinc and copper were initially supplemented with 50-μM concentrations to determine the impact on the production and quality of β-glucuronidase, a lysosomal enzyme, in a parallel bioreactor system. Ethylenediaminetetraacetic acid (EDTA), a metal chelator, was included as another treatment to induce a depletion of trace metal bioavailability to examine deficiency. Samples were drawn daily to monitor cell growth and viability, nutrient levels, β-glucuronidase activity, and trace zinc flux. Cell cycle analysis revealed the inhibition of sub-G0/G1 species in zinc supplemented cultures, maintaining higher viability compared to the control, EDTA-, and copper-supplemented cultures. Enzyme activity analysis in the harvests revealed higher specific activity of β-glucuronidase in reactors supplemented with zinc. A confirmation run was conducted with supplementations of zinc at concentrations of 50, 100, and 150 μM. Further cell cycle analysis and caspase-3 analysis demonstrated the role of zinc as an apoptosis suppressor responsible for the enhanced harvest purity of β-glucuronidase from zinc-supplemented bioreactors.

    更新日期:2020-01-15
  • Quantitative multi-omics analysis of the effects of mitochondrial dysfunction on lipid metabolism in Saccharomyces cerevisiae
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-12
    Xiaopeng Guo, Miaomiao Zhang, Yue Gao, Guozhen Cao, Dong Lu, Wenjian Li

    In this study, combined genome, transcriptome, and metabolome analysis was performed for eight Saccharomyces cerevisiae mitochondrial respiration-deficient mutants. Each mutant exhibited a unique nuclear genome mutation pattern; the nuclear genome mutations, and thus potentially affected genes and metabolic pathways, showed a co-occurrence frequency of ≤ 3 among the eight mutants. For example, only a lipid metabolism-related pathway was likely to be affected by the nuclear genome mutations in one of the mutants. However, large deletions in the mitochondrial genome were the shared characteristic among the eight mutants. At the transcriptomic level, lipid metabolism was the most significantly enriched Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway for differentially expressed genes (DEGs) co-occurring in both ≥ 4 and ≥ 5 mutants. Any identified DEG enriched in lipid metabolism showed the same up-/down-regulated pattern among nearly all eight mutants. Further, 126 differentially expressed lipid species (DELS) were identified, which also showed the same up-/down-regulated pattern among nearly all investigated mutants. It was conservatively demonstrated that the similar change pattern of lipid metabolism in the entire investigated mutant population was attributed to mitochondrial dysfunction. The change spectrum of lipid species was presented, suggesting that the number and change degree of up-regulated lipid species were higher than those of down-regulated lipid species. Additionally, energy storage lipids increased in content and plasma-membrane phospholipid compositions varied in the relative proposition. The results for the genome, transcriptome, and lipidome were mutually validated, which provides quantitative data revealing the roles of mitochondria from a global cellular perspective.

    更新日期:2020-01-15
  • Antimicrobial secondary metabolites from agriculturally important bacteria as next-generation pesticides
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-19
    Chetan Keswani, Harikesh B. Singh, Carlos García-Estrada, John Caradus, Ya-Wen He, Samia Mezaache-Aichour, Travis R. Glare, Rainer Borriss, Estibaliz Sansinenea

    Abstract The whole organisms can be packaged as biopesticides, but secondary metabolites secreted by microorganisms can also have a wide range of biological activities that either protect the plant against pests and pathogens or act as plant growth promotors which can be beneficial for the agricultural crops. In this review, we have compiled information about the most important secondary metabolites of three important bacterial genera currently used in agriculture pest and disease management.

    更新日期:2020-01-15
  • Advances in acrylamide bioproduction catalyzed with Rhodococcus cells harboring nitrile hydratase
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-19
    Song Jiao, Fulong Li, Huimin Yu, Zhongyao Shen

    Acrylamide is an important bulk chemical used for producing polyacrylamide, which is widely applied in diverse fields, such as enhanced oil recovery and water treatment. Acrylamide production with a superior biocatalyst, free-resting Rhodococcus cells containing nitrile hydratase (NHase), has been proven to be simple but effective, thereby becoming the main method adopted in industry to date. Under the harsh industrial conditions, however, NHase-containing Rhodococcus cells in a natural state are prone to deactivation. Thus, multiple genetic strategies able to evolve recombinant Rhodococcus biocatalysts at either the enzyme or cell level have been reported. While most of the methods on enzyme engineering concentrate on NHase stability enhancement by strengthening the flexible sites, Rhodococcus cell engineering with various methods can enhance both the NHase activity and stability as well. Developing some new types of reactors, especially the microreactor, is also an effective way to improve the hydration process efficiency. Compared with the conventional stirred tank reactor, the membrane dispersion microreactor can enhance the heat and mass transfer in the hydration process with Rhodococcus cells as biocatalysts, thereby significantly improving the productivity of the acrylamide bioproduction process.

    更新日期:2020-01-15
  • Metabolic engineering for the production of fat-soluble vitamins: advances and perspectives
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-14
    Panhong Yuan, Shixiu Cui, Yanfeng Liu, Jianghua Li, Guocheng Du, Long Liu

    Fat-soluble vitamins are vitamins that are insoluble in water, soluble in fat, and organic solvents; they are found in minute amount in various foods. Fat-soluble vitamins, including vitamins A, D, E, and K, have been widely used in food, cosmetics, health care products, and pharmaceutical industries. Fat-soluble vitamins are currently produced via biological and chemical synthesis. In recent years, fat-soluble vitamin production by biotechnological routes has been regarded as a very promising approach. Based on biosynthetic pathways, considerable advances of α-tocopherol and β-carotenes have been achieved in transgenic plants and microalgae. Microbial fermentation, as an alternative method for the production of vitamin K and β-carotenes, is attracting considerable attention because it is an environment friendly process. In this review, we address the function and applications of fat-soluble vitamins, and an overview of current developments in the production of fat-soluble vitamins in transgenic plants, microalgae, and microorganisms. We focus on the metabolic and process engineering strategies for improving production of fat-soluble vitamins, and we hope this review can be useful for the people who are interested in the production of fat-soluble vitamins by biotechnological routes.

    更新日期:2020-01-15
  • Enzymatic characterization and regulation of gene expression of PhoK alkaline phosphatase in Sphingobium sp. strain TCM1
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-12
    Shouji Takahashi, Yuka Morooka, Takahito Kumakura, Katsumasa Abe, Yoshio Kera

    Abstract Sphingobium sp. strain TCM1 can significantly degrade chlorinated organophosphorus flame retardants, such as tris(2-chloroethyl) phosphate. The PhoK of strain TCM1 (Sb-PhoK) is the main alkaline phosphatase (APase) that catalyzes the last step in the degradation pathway. Here, we purified and characterized Sb-PhoK produced in E. coli, and analyzed the regulation of Sb-phoK gene expression in strain TCM1. The recombinant Sb-PhoK was produced in the mature form, lacking a putative signal peptide, and formed a homodimer. Purified Sb-PhoK exhibited 384 U/mg of specific activity at 37 °C. The optimum temperature was 50 °C, and Sb-PhoK was completely inactivated when incubated at 60 °C for 10 min. The optimum pH was 10, with stability observed at pH 6.0–10.5. Sb-PhoK was suggested to contain two Ca2+ and one Zn2+ per subunit, but excess addition of Zn2+ into the reaction mixture markedly inhibited the enzyme activity. Sb-PhoK showed phosphatase activity against various phosphorylated compounds, except for bis(p-nitrophenyl) phosphate, indicating that it is a phosphomonoesterase with broad substrate specificity. The Km and kcat for p-nitrophenyl phosphate were 2.31 mM and 1270 s−1, respectively, under optimal conditions. The enzyme was strongly inhibited by vanadate, dithiothreitol, and SDS, but was highly resistant to urea and Triton X-100. Sb-phoK gene expression was regulated by the inorganic phosphate concentration in culture medium, and was induced at a low inorganic phosphate concentration. The deletion of Sb-phoB gene resulted in no induction of Sb-phoK gene even at a low inorganic phosphate concentration, confirming that Sb-PhoK is a member of Pho regulon.

    更新日期:2020-01-15
  • Novel strategy to improve the colonizing ability of Irpex lacteus in non-sterile wheat straw for enhanced rumen and enzymatic digestibility
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-19
    Dongze Niu, Sasa Zuo, Jianjun Ren, Huhetaoli, Mingli Zheng, Di Jiang, Chuncheng Xu

    Pretreatment with white rot fungi is a promising method to enhance the digestibility of lignocelluloses; however, sterilization of feedstocks prior to inoculation is one of the costliest steps. To improve the colonizing ability of white rot fungi under non-sterile condition, Irpex lacteus, Pleurotus ostreatus, and Phanerochaete chrysosporium were inoculated in the wheat straw ensiled for 28 days and incubated for 56 days to determine the changes in microbe counts, organic acid content, chemical composition, and rumen and enzymatic digestibility. Results showed that ensiling produced abundant organic acids and suppressed most microbes in wheat straw. Significant growth of I. lacteus was observed after 3 days of incubation, and molds were only detectable at day 7 in the group. At the end of incubation, aerobic bacteria and lactic acid bacteria decreased by 18% and 38% in the wheat straw treated with I. lacteus, but molds, aerobic bacteria, and lactic acid bacteria thrived in those treated with P. ostreatus and P. chrysosporium. Even more, P. ostreatus and P. chrysosporium increased the lignin content of the ensiled wheat straw by 34% and 65%. However, I. lacteus selectively degraded lignin by 28% and improved the rumen and enzymatic digestibility by 18% and 34%. The finding indicates that ensiling prior to fermentation with I. lacteus is an effective method to control spoilage microbes and to enhance the rumen and enzymatic digestibility of wheat straw.

    更新日期:2020-01-15
  • A plasmid-based genomic screening system for transcriptional regulators of non-adjacent xenobiotic catabolism genes
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-10
    Minggen Cheng, Ziyu Xing, Luyao Lu, Feng Chen, Jian He, Xing Huang

    Bacteria play an important role in the catabolism of environmental xenobiotics. The study of transcriptional regulation has greatly enhanced our understanding of the molecular mechanisms associated with these processes. However, genes encoding transcription factors (TFs) for xenobiotic catabolism are usually not located in the immediate vicinity of the catabolic genes that they regulate; therefore, functional identification of these TFs is difficult. Significantly modified from a metagenome screening method substrate-induced gene expression (SIGEX), here we propose a synthetic pSRGFP-18 plasmid-based tool as a TF reporter system. In short, two multiple cloning sites (MCS) were designed; one in front of an egfp reporter gene was constructed for promoter insertion, and the other MCS was used for shotgun cloning of genomic DNA. Based on the regulatory relationship between TFs and the promoter of their associated catabolic genes, this approach allowed us to screen for TF genes using a genome shotgun approach. This system performed well when testing the known operons. Following statistical analysis of known catabolic operons in Escherichia coli and Bacillus subtilis, the suggested region of the target promoter for this system was from − 250 to + 150. Furthermore, to broaden the applicability of this plasmid, a series of pSRGFP-18 and pBBR1-based pSRGFP-X plasmids were constructed, which had broad host ranges and contained different antibiotic markers. This study outlines a powerful tool to enable functional identification of TFs for bacterial xenobiotic catabolism.

    更新日期:2020-01-15
  • OxyR-controlled surface polysaccharide production and biofilm formation in Acinetobacter oleivorans DR1
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-20
    Bora Shin, Chulwoo Park, Woojun Park

    Abstract The genomes of several Acinetobacter species possess three distinct polysaccharide-producing operons [two poly-N-acetyl glucosamine (PNAG) and one K-locus]. Using a microfluidic device, an increased amount of polysaccharides and enhanced biofilm formation were observed following continuous exposure to H2O2 and removal of the H2O2-sensing key regulator, OxyR, in Acinetobacter oleivorans DR1 cells. Gene expression analysis revealed that genes located in PNAG1, but not those in PNAG2, were induced and that genes in the K-locus were expressed in the presence of H2O2. Interestingly, the expression of the K-locus gene was enhanced in the PNAG1 mutant and vice versa. The absence of either OxyR or PNAG1 resulted in enhanced biofilm formation, higher surface hydrophobicity, and increased motility, implying that K-locus-driven polysaccharide production in both the oxyR and PNAG1 deletion mutants may be related to these phenotypes. Both the oxyR and K-locus deletion mutants were more sensitive to H2O2 compared with the wildtype and PNAG1 mutant strains. Purified OxyR binds to the promoter regions of both polysaccharide operons with a higher affinity toward the K-locus promoter. Although oxidized OxyR could bind to both promoter regions, the addition of dithiothreitol further enhanced the binding efficiency of OxyR, suggesting that OxyR might function as a repressor for controlling these polysaccharide operons.

    更新日期:2020-01-15
  • Production and characterisation of a marine Halomonas surface-active exopolymer
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-07
    Tony Gutierrez, Gordon Morris, Dave Ellis, Barbara Mulloy, Michael D. Aitken

    Abstract During screening for novel emulsifiers and surfactants, a marine gammaproteobacterium, Halomonas sp. MCTG39a, was isolated and selected for its production of an extracellular emulsifying agent, P39a. This polymer was produced by the new isolate during growth in a modified Zobell’s 2216 medium amended with 1% glucose, and was extractable by cold ethanol precipitation. Chemical, chromatographic and nuclear magnetic resonance spectroscopic analysis confirmed P39a to be a high-molecular-weight (~ 261,000 g/mol) glycoprotein composed of carbohydrate (17.2%) and protein (36.4%). The polymer exhibited high emulsifying activities against a range of oil substrates that included straight-chain aliphatics, mono- and alkyl- aromatics and cycloparaffins. In general, higher emulsification values were measured under low (0.1 M PBS) compared to high (synthetic seawater) ionic strength conditions, indicating that low ionic strength is more favourable for emulsification by the P39a polymer. However, as observed with other bacterial emulsifying agents, the polymer emulsified some aromatic hydrocarbon species, as well as refined and crude oils, more effectively under high ionic strength conditions, which we posit could be due to steric adsorption to these substrates as may be conferred by the protein fraction of the polymer. Furthermore, the polymer effected a positive influence on the degradation of phenanthrene by other marine bacteria, such as the specialist PAH-degrader Polycyclovorans algicola. Collectively, based on the ability of this Halomonas high-molecular-weight glycoprotein to emulsify a range of pure hydrocarbon species, as well as refined and crude oils, it shows promise for the bioremediation of contaminated sites.

    更新日期:2020-01-15
  • Genome mining integrating semi-rational protein engineering and nanoreactor design: roadmap for a robust biocatalyst for industrial resolution of Vince lactam
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-11
    Hongxia Li, Shuaihua Gao, Yan Qiu, Chaoqun Liang, Shaozhou Zhu, Guojun Zheng

    Biomanufacturing of chemicals using biocatalysts is an attractive strategy for the production of valuable pharmaceuticals since it is usually more economical and has a much-reduced environmental impact. However, there are often challenges such as their thermal instability that should be overcome before a newly discovered enzyme is eventually translated into industrial processes. In this work, we describe a roadmap for the development of a robust catalyst for industrial resolution of Vince lactam, a key intermediate for the synthesis of carbocyclic-nucleoside-related pharmaceuticals. By a genome mining strategy, a new (+)-γ-lactamase (MiteL) from Microbacterium testaceum was successfully discovered and biochemically characterized. In vitro studies showed that the enzyme exhibited high activity but poor enantioselectivity (E = 6.3 ± 0.2) toward racemic Vince lactam, and thus, it is not suitable for industrial applications. Based on structural modeling and docking studies, a semi-rational engineering strategy combined with an efficient screening method was then applied to improve the enantioselectivity of MiteL. Several mutants with significant shifting stereoselectivity toward (−)-γ-lactam were obtained by site-saturation mutagenesis. Synergy effects led to the final mutant F14D/Q114R/M117L, which enabled efficient acquisition of (−)-γ-lactam with a high E value (> 200). The mutant was biochemically characterized, and the docking studies suggested a plausible mechanism for its improved selectivity. Finally, a sunflower-like nanoreactor was successfully constructed to improve the mutant’s robustness via protein supramolecular self-assembly. Thus, the synergism between semi-rational protein engineering and self-assembling immobilization enabled construction of a nanoreactor with superior properties, which can be used for resolution of Vince lactam in large scale.

    更新日期:2020-01-15
  • Evaluation of the protective immunity of Riemerella anatipestifer OmpA
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-21
    Xinxin Xu, Yaohui Xu, Shuang Miao, Pan Jiang, Junsheng Cui, Yanshan Gong, Panpan Tan, Xiaoli Du, Nazrul Islam, Qinghai Hu

    Riemerella anatipestifer is responsible for an economically important disease of commercially raised ducks. No or only few cross-protection was observed between different serotypes of R. anatipestifer strains, and so far no protective antigen in this bacterium has been identified. OmpA is a predominant immunogenic protein of R. anatipestifer, and within the 1467 bp ompA ORF (ompA1467), there is another 1164 bp ORF (ompA1164) with the same C-terminal. In this study, our results showed that the full sequence of ompA1467 from some R. anatipestifer strains with different serotypes shared the same amino acid sequence. Animal experiments showed that the soluble recombinant protein rOmpA1164, but not rOmpA1467, could provide partial protective immunity against challenge. Moreover, there was no significant difference in protective immunity between ducklings immunized with Th4△ompA bacterin and those immunized with Th4 bacterin. In addition, OmpA1467 was the main existing form of OmpA in R. anatipestifer cells by gel electrophoresis and western blot analyses. The results suggested that OmpA1467 was not a protective antigen of R. anatipestifer, and antibodies against proteins other than OmpA play a critical role in the process of anti-R. anatipestifer infection.

    更新日期:2020-01-15
  • Characterization of three GH35 β-galactosidases, enzymes able to shave galactosyl residues linked to rhamnogalacturonan in pectin, from Penicillium chrysogenum 31B
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-18
    Tatsuya Kondo, Yuichi Nishimura, Kaori Matsuyama, Megumi Ishimaru, Masami Nakazawa, Mitsuhiro Ueda, Tatsuji Sakamoto

    Abstract Three recombinant β-galactosidases (BGALs; PcBGAL35A, PcBGAL35B, and PcGALX35C) belonging to the glycoside hydrolase (GH) family 35 derived from Penicillium chrysogenum 31B were expressed using Pichia pastoris and characterized. PcBGAL35A showed a unique substrate specificity that has not been reported so far. Based on the results of enzymological tests and 1H-nuclear magnetic resonance, PcBGAL35A was found to hydrolyze β-1,4-galactosyl residues linked to l-rhamnose in rhamnogalacturonan-I (RG-I) of pectin, as well as p-nitrophenyl-β-d-galactopyranoside and β-d-galactosyl oligosaccharides. PcBGAL35B was determined to be a common BGAL through molecular phylogenetic tree and substrate specificity analysis. PcGALX35C was found to have similar catalytic capacities for the β-1,4-galactosyl oligomer and polymer. Furthermore, PcGALX35C hydrolyzed RG-I-linked β-1,4-galactosyl oligosaccharide side chains with a degree of polymerization of 2 or higher in pectin. The amino acid sequence similarity of PcBGAL35A was approximately 30% with most GH35 BGALs, whose enzymatic properties have been characterized. The amino acid sequence of PcBGAL35B was approximately 80% identical to those of BGALs from Penicillium sp. The amino acid sequence of PcGALX35C was classified into the same phylogenetic group as PcBGAL35A. Pfam analysis revealed that the three BGALs had five domains including a catalytic domain. Our findings suggest that PcBGAL35A and PcGALX35C are enzymes involved in the degradation of galactosylated RG-I in pectin. The enzymes characterized in this study may be applied for products that require pectin processing and for the structural analysis of pectin.

    更新日期:2020-01-15
  • Modulation effect of tea consumption on gut microbiota
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-18
    Yu-Chuan Liu, Xin-Yu Li, Liang Shen

    Tea is one of the most popular beverages in the world and possesses a wide range of beneficial effects for human health. The modulation of tea on gut microbiota has gained much interest in recent years. The present study discussed the modulation effect of various types of tea on gut microbiota, which plays crucial roles in human health, as investigated by in vitro animal and human studies. The currently available findings from a total of 23 studies support the modulation effects of tea liquid, tea extract, and its major active components, including polyphenols, polysaccharides, and teasaponin, on gut microbiota. Overall, tea possesses prebiotic-like effect and can alleviate the gut microbiota dysbiosis induced by high-fat diet in gut microbiota, despite the detailed bacterial taxa may alter depending on the types of tea supplemented. Current evidence implies that the modulation effect on gut microbiota may be an important action mechanism underlying the beneficial effect of tea consumption in daily life and also the great potential of strategically chosen tea extract to develop functional foods.

    更新日期:2020-01-15
  • Chemoenzymatic synthesis of the pH responsive surfactant octyl β-D-glucopyranoside uronic acid
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2019-12-07
    Ngoc T. N. Ngo, Carl Grey, Patrick Adlercreutz

    Methodology was developed to expand the range of benign alkyl glycoside surfactants to include also anionic types. This was demonstrated possible through conversion of the glycoside to its carboxyl derivative. Specifically, octyl β-D-glucopyranoside (OG) was oxidised to the corresponding uronic acid (octyl β-D-glucopyranoside uronic acid, OG-COOH) using the catalyst system T. versicolor laccase/2,2,6,6-tetramethylpiperidinyloxy (TEMPO) and oxygen from air as oxidant. The effects of oxygen supply methodology, concentrations of laccase, TEMPO and OG as well as reaction temperature were evaluated. At 10 mM substrate concentration, the substrate was almost quantitatively converted into product, and even at a substrate concentration of 60 mM, 85% conversion was reached within 24 h. The surfactant properties of OG-COOH were markedly dependent on pH. Foaming was only observed at low pH, while no foam was formed at pH values above 5.0. Thus, OG-COOH can be an attractive low-foaming surfactant, for example for cleaning applications and emulsification, in a wide pH range (pH 1.5–10.0).

    更新日期:2020-01-15
  • Correction to: Heterologous production of chlortetracycline in an industrial grade Streptomyces rimosus host
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-14
    Xuefeng Wang, Shouliang Yin, Jing Bai, Yang Liu, Keqiang Fan, Huizhuan Wang, Fang Yuan, Baohua Zhao, Zilong Li, Weishan Wang

    The original version of this article contains an error.

    更新日期:2020-01-14
  • Transgene suppression in plants by foliar application of in vitro-synthesized small interfering RNAs
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-14
    Alexandra S. Dubrovina, Olga A. Aleynova, Andrey R. Suprun, Zlata V. Ogneva, Konstantin V. Kiselev

    Abstract Recent research has shown that plants can uptake long dsRNAs and dsRNA-derived siRNAs that target important genes of infecting fungi or viruses when applied on the surface of plant leaves. The external RNAs were capable of local and systemic movement inducing plant resistance against the pathogens. Few studies have been made for plant gene regulation by foliar application of RNAs. In this study, several types of ssRNA and siRNA duplexes targeting the neomycin phosphotransferase II (NPTII) transgene were in vitro-synthesized and externally applied to the leaf surface of 4-week-old transgenic Arabidopsis thaliana plants. External application of the synthetic NPTII-encoding siRNAs down-regulated NPTII transcript levels in transgenic A. thaliana 1 and 7 days post-treatment with a higher and more consistent effect being observed for siRNAs methylated at 3′ ends. We also analyzed the effects of external NPTII-encoding dsRNA precursors and a dsRNA-derived heterogenous siRNA mix. Digestion of the NPTII-dsRNA to the heterogeneous siRNAs did not improve efficiency of the transgene suppression effect. Key Points• Foliar application of siRNAs down-regulated a commonly used transgene in Arabidopsis. • A more consistent effect was observed for methylated siRNAs. • The findings are important for development of plant gene regulation approaches.

    更新日期:2020-01-14
  • Significant improvement of the enantioselectivity of a halohydrin dehalogenase for asymmetric epoxide ring opening reactions by protein engineering
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-14
    Feng Xue, Li-Hui Zhang, Qing Xu

    Abstract Halohydrin dehalogenases (HHDHs) have attracted much attention due to their ability to synthesize enantiomerically enriched epoxides and β-haloalcohols. However, most of the HHDHs exhibit low enantioselectivity. Here, a HHDH from the alphaproteobacteria isolate 46_93_T64 (AbHHDH), which shows only poor enantioselectivity in the catalytic resolution of rac-PGE (E = 9.9), has been subjected to protein engineering to enhance its enantioselectivity. Eight mutants (R89K, R89Y, V137I, P178A, N179Q, N179L, F187L, F187A) showed better enantioselectivity than the wild type. The best single mutant N179L (E = 93.0) showed a remarkable 9.4-fold increase in the enantioselectivity. Then, the single mutations were combined to produce the double, triple, quadruple, and quintuple mutants. Among the combinational mutants, the best variant (R89Y/N179L) showed an increased E value of up to 48. The E values of the variants N179L and R89Y/N179L for other epoxides 2–7 were 12.2 to > 200, which showed great improvement compared to 1.2 to 10.5 for the wild type. Using the variant N179L, enantiopure (R)-PGE with > 99% ee could be readily prepared, affording a high yield and a high concentration.

    更新日期:2020-01-14
  • Colletotrichum: species complexes, lifestyle, and peculiarities of some sources of genetic variability
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-14
    Leandro Lopes da Silva, Hanna Lorena Alvarado Moreno, Hilberty Lucas Nunes Correia, Mateus Ferreira Santana, Marisa Vieira de Queiroz

    Abstract The genus Colletotrichum comprises species with different lifestyles but is mainly known for phytopathogenic species that infect crops of agronomic relevance causing considerable losses. The fungi of the genus Colletotrichum are distributed in species complexes and within each complex some species have particularities regarding their lifestyle. The most commonly found and described lifestyles in Colletotrichum are endophytic and hemibiotrophic phytopathogenic. Several of these phytopathogenic species show wide genetic variability, which makes long-term maintenance of resistance in plants difficult. Different mechanisms may play an important role in the emergence of genetic variants but are not yet fully understood in this genus. These mechanisms include heterokaryosis, a parasexual cycle, sexual cycle, transposable element activity, and repeat-induced point mutations. This review provides an overview of the genus Colletotrichum, the species complexes described so far and the most common lifestyles in the genus, with a special emphasis on the mechanisms that may be responsible, at least in part, for the emergence of new genotypes under field conditions.

    更新日期:2020-01-14
  • Discovery and mechanism of intestinal bacteria in enzymatic cleavage of C–C glycosidic bonds
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-13
    Bin Wei, Ya-Kun Wang, Wen-Hui Qiu, Si-Jia Wang, Yue-Hong Wu, Xue-Wei Xu, Hong Wang

    C-Glycosides, a special type of glycoside, are frequently distributed in many kinds of medicinal plants, such as puerarin and mangiferin, showing various and significant bioactivities. C-Glycosides are usually characterized by the C–C bond that forms between the anomeric carbon of sugar moieties and the carbon atom of aglycon, which is usually resistant against acidic hydrolysis and enzymatic treatments. Interestingly, C-glycosides could be cleaved by several intestinal bacteria, but whether the enzymatic cleavage of C–C glycosidic bond is reduction or hydrolysis has been controversial; furthermore, whether existence of a “C-glycosidase” directly catalyzing the cleavage is not clear. Here we review research advances about the discovery and mechanism of intestinal bacteria in enzymatic cleavage of C–C glycosidic bond with an emphasis on the identification of enzymes manipulation the deglycosylation. Finally, we give a brief conclusion about the mechanism of C-glycoside deglycosylation and perspectives for future study in this field.

    更新日期:2020-01-13
  • Two new ene-reductases from photosynthetic extremophiles enlarge the panel of old yellow enzymes: Ct OYE and Gs OYE
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-13
    Marina Simona Robescu, Mattia Niero, Mélanie Hall, Laura Cendron, Elisabetta Bergantino

    Looking for new ene-reductases with uncovered features beneficial for biotechnological applications, by mining genomes of photosynthetic extremophile organisms, we identified two new Old Yellow Enzyme homologues: CtOYE, deriving from the cyanobacterium Chroococcidiopsis thermalis, and GsOYE, from the alga Galdieria sulphuraria. Both enzymes were produced and purified with very good yields and displayed catalytic activity on a broad substrate spectrum by reducing α,β-unsaturated ketones, aldehydes, maleimides and nitroalkenes with good to excellent stereoselectivity. Both enzymes prefer NADPH but demonstrate a good acceptance of NADH as cofactor. CtOYE and GsOYE represent robust biocatalysts showing high thermostability, a wide range of pH optimum and good co-solvent tolerance. High resolution X-ray crystal structures of both enzymes have been determined, revealing conserved features of the classical OYE subfamily as well as unique properties, such as a very long loop entering the active site or an additional C-terminal alpha helix in GsOYE. Not surprisingly, the active site of CtOYE and GsOYE structures revealed high affinity toward anions caught from the mother liquor and trapped in the anion hole where electron-withdrawing groups such as carbonyl group are engaged. Ligands (para-hydroxybenzaldehyde and 2-methyl-cyclopenten-1-one) added on purpose to study complexes of GsOYE were detected in the enzyme catalytic cavity, stacking on top of the FMN cofactor, and support the key role of conserved residues and FMN cofactor in the catalysis.

    更新日期:2020-01-13
  • Production, characterization, and application of a monoclonal antibody specific for the extracellular domain of human P2X7R
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-13
    Mingxuan Li, Shuping Luo, Yunfang Zhang, Lina Jia, Chuanyu Yang, Xiaoxiang Peng, Ronglan Zhao

    This paper focuses on the production of a high-affinity monoclonal antibody (mAb) that can efficiently detect and block purinergic ligand-gated ion channel 7 receptor (P2X7R). To achieve this goal, the extracellular domain of human P2X7R, P2X7R-ECD, was used as an immunogen for BALB/c mice, inducing them to produce spleen lymphocytes that were subsequently fused with myeloma cells. Screening of the resultant hybridoma clones resulted in the selection of one stable positive clone that produced a qualified mAb, named 4B3A4. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis demonstrated that the purity of the purified 4B3A4 mAb was above 85%, with prominent bands corresponding to molecular weights of 55 kDa (heavy chain) and 25 kDa (light chain), and the BCA assay showed that the concentration of the purified 4B3A4 mAb was 0.3 mg/mL. Western blot analysis revealed that the 4B3A4 mAb could specifically recognize and bind both P2X7R-ECD and the full-length P2X7R protein. Laser scanning confocal microscopy (LSCM) revealed that the 4B3A4 mAb specifically bound to P2X7R on the membrane of human peripheral blood mononuclear cells (PBMCs). P2X7R expression was significantly different between healthy individuals and people with certain cancers as determined by flow cytometry (FCM). In addition, the 4B3A4 mAb significantly reduced ATP-stimulated Ca2+ entry and YO-PRO-1 uptake, which indicated that the 4B3A4 mAb effectively blocked P2X7R activity. These data indicate that the 4B3A4 mAb can be further used as not only an antibody to detect cell surface P2X7R but also as a therapeutic antibody to target P2X7R-related signaling pathways.

    更新日期:2020-01-13
  • Identification of Zur boxes and determination of their roles in the differential regulation of the Zur regulon in Agrobacterium tumefaciens C58
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-11
    Puttamas Nuonming, Sasimaporn Khemthong, Rojana Sukchawalit, Skorn Mongkolsuk

    Zinc uptake regulator (Zur) is a transcriptional regulator that represses zinc acquisition genes under high zinc conditions. The aim of this study was to identify and investigate the role of Zur-binding motifs (Zur boxes) in the differential regulation of Zur target genes, including the zinT, znuA, znuCB-zur operon, the troCBA operon, and yciC, in Agrobacterium tumefaciens. DNase I footprinting and gel shift assays were performed, confirming that Zur directly binds to 18-bp inverted repeat motifs found in the promoter of these Zur-regulated genes. Furthermore, promoter-lacZ fusions and mutagenesis of the identified Zur boxes were performed to assess the role of each Zur box. A Zur box found in the zinT promoter was required for zinc-dependent repression by Zur. The intergenic region between the znuA gene and the znuCB-zur operon contains two Zur boxes, named A and C, which immediately precede the genes znuA and znuC, respectively. Zur box A, but not Zur box C, was essential for the repression of the znuA promoter. Both Zur boxes A and C were implicated in the repression of the znuC promoter, in which mutation of either box alone was sufficient for full derepression of the znuC promoter. Three Zur boxes named T, M, and Y were identified in the intergenic region between the troCBA operon and the yciC gene. Zur box Y, which immediately precedes yciC, was shown to be responsible for Zur repression of the yciC promoter. In contrast, two Zur boxes, T and M, were essential for the complete repression of the troCBA operon, and full derepression of the troC promoter was exhibited when both Zur boxes were mutated simultaneously. Sequence analysis of the identified Zur boxes revealed a correlation between deviation from the core recognition sequence of the Zur box and the requirement of two Zur boxes for Zur regulation of distinctive promoters.

    更新日期:2020-01-13
  • Prevention of biofilm formation by quorum quenching
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-11
    E. Paluch, J. Rewak-Soroczyńska, I. Jędrusik, E. Mazurkiewicz, K. Jermakow

    Quorum sensing (QS) is a mechanism that enables microbial communication. It is based on the constant secretion of signaling molecules to the environment. The main role of QS is the regulation of vital processes in the cell such as virulence factor production or biofilm formation. Due to still growing bacterial resistance to antibiotics that have been overused, it is necessary to search for alternative antimicrobial therapies. One of them is quorum quenching (QQ) that disrupts microbial communication. QQ-driving molecules can decrease or even completely inhibit the production of virulence factors (including biofilm formation). There are few QQ strategies that comprise the use of the structural analogues of QS receptor autoinductors (AI). They may be found in nature or be designed and synthesized via chemical engineering. Many of the characterized QQ molecules are enzymes with the ability to degrade signaling molecules. They can also impede cellular signaling cascades. There are different techniques used for testing QS/QQ, including chromatography-mass spectroscopy, bioluminescence, chemiluminescence, fluorescence, electrochemistry, and colorimetry. They all enable qualitative and quantitative measurements of QS/QQ molecules. This article gathers the information about the mechanisms of QS and QQ, and their effect on microbial biofilm formation. Basic methods used to study QS/QQ, as well as the medical and biotechnological applications of QQ, are also described. Basis research methods are also described as well as medical and biotechnological application.

    更新日期:2020-01-13
  • Phenotypic and genomic analysis of multiple heavy metal–resistant Micrococcus luteus strain AS2 isolated from industrial waste water and its potential use in arsenic bioremediation
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-11
    Shahid Sher, Syed Zajif Hussain, Abdul Rehman

    Multiple heavy metal–resistant bacterium, Micrococcus luteus strain AS2, was isolated from industrial waste water of District Sheikhupura, Pakistan. The isolated bacterium showed minimum inhibitory concentrations of 55 and 275 mM against arsenite and arsenate. The bacterial strain also showed resistance against other heavy metal ions, i.e., lead, cadmium, chromium, mercury, nickel, and zinc, apart from arsenic. The optimum temperature and pH were 37 °C and 7, respectively. The antioxidant enzymes such as catalase were significantly increased under arsenite stress. The increase in 43.9% of GSH/GSSG and 72.72% of non-protein thiol was determined under15 mM arsenite stress. Bacterial genome was sequenced through Illumina and Nanopore and genes related to arsenic and other heavy metals were identified and blast (tblastx) on NCBI. Through scanning electron microscopy, no morphological changes were observed in bacterial cells under arsenite stress. The peaks appeared in EDX showed that there is surface adsorption of arsenite in bacterial cell while it was confirmed from Fourier transformed infrared spectroscopy analysis that there is some interaction between arsenite and functional groups present on the surface of bacterial cell. The SDS-PAGE analysis of whole-cell proteins under 15 mM arsenite stress clearly revealed that there is upregulation of some proteins in ranged of 60 to 34 kDa. The bioremediation efficiency (E) of bacterial biomass was 72% after 2 h and 99% after 10 h. The bioremediation efficiency of bacterial biomass is an indicator for the isolated bacterium to employ as a potential candidate for the amelioration of sites contaminated with arsenic.

    更新日期:2020-01-13
  • Effects of pH, temperature and salinity on P3HB synthesis culturing the marine Rhodovulum sulfidophilum DSM-1374
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-11
    Pietro Carlozzi, Tiziana Di Lorenzo, Demetrios F. Ghanotakis, Eleftherios Touloupakis

    Rhodovulum sulfidophilum DSM-1374 is a potential producer of polyester when growing in phototrophic conditions. The present study investigated on a polyester product (P3HB) by culturing Rhodovulum sulfidophilum DSM-1374 in two different photobioreactors (PBR-1 and PBR-2) both with 4-L working volumes. PBR-1 is equipped with an internal rotor having 4 paddles to mix the bacterial culture while PBR-2 has an internal coil-shaped rotor. After selecting PBR-1, which best performed in the preliminary experiment, the effect of different stressing growth conditions as pH (7.0, 8.0, and 9.0), temperature (25, 30, and 35 °C), and medium salinity (1.5, 2.5, 3.5, and 4.5%) were tested. When the pH of the culture was set to 8.0, the capability of the bacterium to synthetize the polyester increased significantly reaching a concentration of 412 mg (P3HB)/L; the increase of the pH at 9.0 caused a reduction of the P3HB concentration in the culture. The medium salinity of 4.5% was the best stress-growth condition to reach the highest concentration of polyester in the culture (820 ± 50 mg (P3HB)/L) with a P3HB mass fraction in the dry biomass of 33 ± 1.5%. Stresses caused by culture temperature are another potential parameter that could increase the synthesis of P3HB.

    更新日期:2020-01-13
  • A tandem GGDEF-EAL domain protein-regulated c-di-GMP signal contributes to spoilage-related activities of Shewanella baltica OS155
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-11
    Feifei Wang, Yongzheng Wang, Congnan Cen, Linglin Fu, Yanbo Wang

    Cyclic diguanylate (c-di-GMP) is a second messenger involved in the regulation of various physiological processes in bacteria. However, its function in spoilage bacteria has not yet been addressed. Here, we studied the function of a tandem GGDEF-EAL domain protein, Sbal_3235, in the spoilage bacterium Shewanella baltica OS155. The deletion of sbal_3235 significantly reduced the c-di-GMP level, biofilm formation, and exopolysaccharide, trimethylamine (TMA), and putrescine production; sbal_3235 deletion also downregulated the expression of the torS and speF genes and affected membrane fatty acid composition. Site-directed mutagenesis in conserved GGDEF and EAL motifs abolished diguanylate cyclase (DGC) and phosphodiesterase (PDE) activity, respectively. These data indicate that Sbal_3235 is an essential contributor to the c-di-GMP pool with bifunctional DGC and PDE activity, which is involved in the biofilm formation and spoilage activity of S. baltica OS155. Our findings expand the biochemical role of c-di-GMP and uncover its link to spoilage activities, providing novel targets for food quality and safety controlling.

    更新日期:2020-01-13
  • Naproxen in the environment: its occurrence, toxicity to nontarget organisms and biodegradation
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-10
    Danuta Wojcieszyńska, Urszula Guzik

    Abstract This article summarizes the current knowledge about the presence of naproxen in the environment, its toxicity to nontarget organisms and the microbial degradation of this drug. Currently, naproxen has been detected in all types of water, including drinking water and groundwater. The concentrations that have been observed ranged from ng/L to μg/L. These concentrations, although low, may have a negative effect of long-term exposure on nontarget organisms, especially when naproxen is mixed with other drugs. The biological decomposition of naproxen is performed by fungi, algae and bacteria, but the only well-described pathway for its complete degradation is the degradation of naproxen by Bacillus thuringiensis B1(2015b). The key intermediates that appear during the degradation of naproxen by this strain are O-desmethylnaproxen and salicylate. This latter is then cleaved by 1,2-salicylate dioxygenase or is hydroxylated to gentisate or catechol. These intermediates can be cleaved by the appropriate dioxygenases, and the resulting products are incorporated into the central metabolism. Key points •High consumption of naproxen is reflected in its presence in the environment. •Prolonged exposure of nontargeted organisms to naproxen can cause adverse effects. •Naproxen biodegradation occurs mainly through desmethylnaproxen as a key intermediate.

    更新日期:2020-01-11
  • Bionanomining: biotechnological synthesis of metal nanoparticles from mining waste—opportunity for sustainable management of mining environmental liabilities
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-10
    Liey-si Wong-Pinto, Andrew Menzies, Javier I. Ordóñez

    Abstract Mining is an important activity for many countries, especially some in development, such as Chile, where it is a pillar of its economy. However, it generates large impacts that are undesirable for the population such as the generation of polluting solid and effluents with a high content of heavy metals and metalloids, which are traditionally accumulated in deposits. In recent years, bionanomining emerged as a cutting-edge scientific-technological development associated with the application of micro- and macro-organisms to generate nanotechnological products by using mining and industrial wastes and wastewaters. Biomass of many species of bacteria, plants, algae and fungi have the ability to reduce or oxidise cations, which can physically be deposited as nanometric materials such as the nanoparticles. Nanoparticles are materials that are increasingly used, and therefore, their demand increase, based on the high surface area characteristics to improve thermal, electrical and optical properties of materials, and metallic ones have also antimicrobial activity. This review addresses the biosynthesis of metal nanoparticles, focusing on mining waste recovery strategies, which is an emerging reality in mining countries. Transformation of potentially hazardous waste into a valuable product through techniques that are eco-friendly is an opportunity to develop sustainably depressed or polluted sites.

    更新日期:2020-01-11
  • Diverse and common features of trehalases and their contributions to microbial trehalose metabolism
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-10
    Masayoshi Sakaguchi

    Trehalose is a stable disaccharide that consists of two glucose units linked primarily by an α,α-(1 → 1)-linkage, and it has been found in a wide variety of organisms. In these organisms, trehalose functions not only as a source of carbon energy but also as a protector against various stress conditions. In addition, this disaccharide is attractive for use in a wide range of applications due to its bioactivities. In trehalose metabolism, direct trehalose-hydrolyzing enzymes are known as trehalases, which have been reported for bacteria, archaea, and eukaryotes, and are classified into glycoside hydrolase 37 (GH37), GH65, and GH15 families according to the Carbohydrate-Active enZyme (CAZy) database. The catalytic domains (CDs) of these enzymes commonly share (α/α)6-barrel structures and have two amino acid residues, Asp and/or Glu, that function as catalytic residues in an inverting mechanism. In this review, I focus on diverse and common features of trehalases within different GH families and their contributions to microbial trehalose metabolism.

    更新日期:2020-01-11
  • A putative mechanism underlying secondary metabolite overproduction by Streptomyces strains with a 23S rRNA mutation conferring erythromycin resistance
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-10
    Kanata Hoshino, Yu Imai, Keiichiro Mukai, Ryoko Hamauzu, Kozo Ochi, Takeshi Hosaka

    Mutations in rrn encoding ribosomal RNA (rRNA) and rRNA modification often confer resistance to ribosome-targeting antibiotics by altering the site of their interaction with the small (30S) and large (50S) subunits of the bacterial ribosome. The highly conserved central loop of domain V of 23S rRNA (nucleotides 2042–2628 in Escherichia coli; the exact position varies by species) of the 50S subunit, which is implicated in peptidyl transferase activity, is known to be important in macrolide interactions and resistance. In this study, we identified an A2302T mutation in the rrnA-23S rRNA gene and an A2281G mutation in the rrnC-23S rRNA gene that were responsible for resistance to erythromycin in the model actinomycete Streptomyces coelicolor A3(2) and its close relative Streptomyces lividans 66, respectively. Interestingly, genetic and phenotypic characterization of the erythromycin-resistant mutants indicated a possibility that under coexistence of the 23S rRNA mutation and mutations in other genes, S. coelicolor A3(2) and S. lividans 66 can produce abundant amounts of the pigmented antibiotics actinorhodin and undecylprodigiosin depending on the combinations of mutations. Herein, we report the unique phenomenon occurring by unexpected characteristics of the 23S rRNA mutations that can affect the emergence of additional mutations probably with an upswing in spontaneous mutations and enrichment in their variations in Streptomyces strains. Further, we discuss a putative mechanism underlying secondary metabolite overproduction by Streptomyces strains with a 23S rRNA mutation conferring erythromycin resistance.

    更新日期:2020-01-11
  • Poly(lactic acid)/carvacrol-based materials: preparation, physicochemical properties, and antimicrobial activity
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-10
    Roberto Scaffaro, Andrea Maio, Antonia Nostro

    Abstract The current demand for new antimicrobial systems has stimulated research for the development of poly(lactic acid)/carvacrol (PLA/CAR)-based materials able to hinder the growth and spread of microorganisms. The eco-friendly characteristics of PLA and cytocompatibility make it very promising in the perspective of green chemistry applications as material for food and biomedical employments. The broad-spectrum biological and pharmacological properties of CAR, including antimicrobial activity, make it an interesting bioactive molecule that can be easily compounded with PLA by adopting the same techniques as those commonly used for PLA manufacturing. This review critically discusses the most common methods to incorporate CAR into a PLA matrix and their interference on the morphomechanical properties, release behavior, and antimicrobial activity of systems. The high potential of PLA/CAR materials in terms of chemical-physical and antimicrobial properties can be exploited for the future development of food packaging, coated medical devices, or drug delivery systems.

    更新日期:2020-01-11
  • Novel mutagenesis and screening technologies for food microorganisms: advances and prospects
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-09
    Qinghui Yu, Yuncheng Li, Bo Wu, Wei Hu, Mingxiong He, Guoquan Hu

    Abstract Microorganisms are indispensable in the food industry, but wild-type strains hardly meet the current industrial demands due to several undesirable traits. Therefore, microbial strain improvement offers a critical solution to enhance the food industry. Traditional techniques for food microbial improvement, such as the use of chemical mutagens and manual isolation/purification, are inefficient, time-consuming, and laborious, restricting further progress in the area of food fermentation. In this review, the applications of novel mutagenesis and screening technologies used for the improvement of food microbes were summarized, including random mutagenesis based on physical irradiation, microbial screening facilitated by a microtiter plate, fluorescence-activated cell or droplet sorting, and microscaled fermentation in a microtiter plate or microbioreactor. In comparison with conventional methods, these new tools have the potential in accelerating microbial strain improvement and their combined applications could create a new trend for strain development. However, several problems that could affect its potential application may include the following: the lack of specific mutagenesis devices and biosensing systems, the insufficient improvement of the mixed culture system, the low efficiency when using filamentous fungi and flocculating bacteria, and the insufficient safety assessment on harnessing genome-editing technology. Therefore, future works on strain improvement remain challenging for the food industry.

    更新日期:2020-01-09
  • New insights on the colonization of the human gut by health-promoting bacteria
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-08
    Sinead T. Morrin, Rita M. Hickey

    We are beginning to see how the microbiota of the human gastrointestinal tract (GIT) can drive the development of new products to benefit human health and wellbeing. Despite the growing market for prebiotics and probiotics, there are currently no commercial products available that aid or increase the attachment of health-promoting bacteria to the gut mucosal surface. Components in milk have the potential to increase commensal adherence in the gut by priming the bacteria or the mucosal surface for colonization. Such compositions have potential for supplementation in many products aimed at individuals at different life stages or those suffering from various disease states where lower numbers of health-promoting bacteria such as bifidobacteria are evident. This review will explore how milk ingredients may lead to the attachment of larger numbers of bacteria with health-promoting properties in the gut.

    更新日期:2020-01-08
  • Encapsulation of live marine bacteria for use in aquaculture facilities and process evaluation using response surface methodology
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-08
    Susana Prado, Juan L. Barja, Asteria Luzardo, Javier Dubert, José Blanco

    New strategies are being proposed in marine aquaculture to use marine bacteria as alternative to antibiotics, as nutritional additive or as immune-stimulant. These approaches are particularly promising for larval and juvenile cultures. In many cases, the bacteria are released in the seawater, where they have to be at appropriate concentrations. In addition, only low-cost technologies are sustainable for this industry, without any complex requirements for use or storage. In this work, we explore the possibilities of preservation of a potential marine probiotic bacterium (Phaeobacter PP-154) as a product suitable for use in marine aquaculture by addition to the seawater. A method which guaranteed the preservation of the viable marine bacteria in a saline medium and their rapid release in the seawater was searched for. In a previous step, classical procedures (freeze-drying and freezing) had been explored, but undesirable results of the interaction of the products obtained with natural seawater led to investigate alternatives. We report the results of the immobilization of the marine bacteria in calcium alginate beads. The final product complies the salinity which allows the requirements of the bacteria without interference with alginate in the formation of beads, and a balanced hardness to retain the bacteria and to be easily released in the marine aquaculture environment. The process was evaluated using the central composite rotatable design (CCRD), a standard response surface methodology (RSM).

    更新日期:2020-01-08
  • Bovine serum albumin affects N-glycoforms of murine IgG monoclonal antibody purified from hybridoma supernatants
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-08
    Jinyu Zhou, Huanyu Gao, Wenchun Xie, Yan Li

    Immunoglobulin G (IgG) is a class of monoclonal antibodies (mAbs) commonly produced in mammalian cell lines. These cell lines are grown in finely adjusted culture media, which contain components that may impact glycoforms. As variation of N-glycoforms can impact the biological properties of IgGs, medium composition should be controlled. Here, we studied the effects on IgG N-glycoforms of different components in hybridoma culture media, specifically compared bovine serum albumin (BSA) with other small molecules, using a matrix-assisted laser desorption/ionization quadrupole ion trap time-of-flight multistage mass spectrometry (MALDI-QIT-TOF MSn)–based approach. We show that small molecular additives caused little change in glycan species, though a number of these reagents, especially glutamine, affected levels of glycosylation. In comparison, the addition of macromolecular protein BSA significantly changed IgG N-glycan patterns, not only in species but also in glycosylation levels. Together, our finding suggests that BSA increases the complexity of IgG N-glycoforms, thus raising the difficulty in maintaining glycoforms consistency during antibody production. Therefore, the effect of BSA on IgG N-glycans should be considered when designing optimal medium formulations for IgG production.

    更新日期:2020-01-08
  • Rapid environmental change shapes pond water microbial community structure and function, affecting mud crab ( Scylla paramamosain ) survivability
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-08
    Yiqin Deng, Changhong Cheng, Juan Feng, Songlin Liu, Hongling Ma, Xiaolong Chen, HaoXiang Chen, Zhixun Guo

    Abstract The aquatic microbial community is sensitive to environmental change; however, the impacts of those changes combined with disease outbreaks affecting S. paramamosain are unknown. Thus, from March to October, we explored the interaction between aquacultural environmental conditions and microbial composition and function in open-air aquaculture ponds containing S. paramamosain in Southern China. The microbial community structure was significantly positively correlated with microbial community function. The environment variables such as temperature and salinity during May and June changed more quickly compared with other periods, resulting changes in the structure and function of the microbial community affected S. paramamosain survivability, with higher crab mortality observed from May to June compared with other periods. These included changes in the relative abundance of Microtrichales, Synechococcales, Rhodobacterales, Chitinophagales, and SAR11_clade, and corresponding functions associated with glycolysis and/or gluconeogenesis, porphyrin and chlorophyll metabolism, photosynthetic proteins, and transcription factors. These changes could impact S. paramamosain mortality and be used to evaluate the health status of the ponds. Though the environment variables during July~October changed slowly comparing to May and June, the ponds microflora changed which benefit S. paramamosain survivability with correspondingly low S. paramamosain mortality. Therefore, rapid environmental change alters the structure and function of the aquatic microflora, increasing S. paramamosain mortality.

    更新日期:2020-01-08
  • The small RNA chaperone Hfq is a critical regulator for bacterial biosynthesis of selenium nanoparticles and motility in Rahnella aquatilis
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-08
    Qiaolin Xu, Yanzhao Song, Zhiqing Lin, Gary Bañuelos, Yanyun Zhu, Yanbin Guo

    Abstract The RNA chaperone, Hfq, is a global post-transcriptional regulator that plays an important role in regulating pleiotropic functions, such as cell growth and motility, stress tolerance, and virulence to host, in many Gram-negative bacteria. This study examined the functional roles of Hfq in Rahnella aquatilis HX2, a plant beneficial, selenium nanoparticles (SeNPs)–producing soil bacterium. A mutant HX2∆hfq with an in-frame deletion within the hfq gene in R. aquatilis HX2 was constructed and tested for various phenotypic features. Bacterial growth, motility, selenite reduction, and SeNPs production were compared between the mutant, the wild-type, and the complementation strain. The hfq gene deletion delayed the growth of strain HX2, with a lower bacterial population during the stationary phase, and significantly impaired the swimming motility of the bacterium, showing a smaller motility ring on the plate. The hfq mutation also dramatically declined microbial-induced reduction of selenite and SeNPs production in HX2, which was independent of cell growth. The introduction of a trans-expressed hfq gene into HX2∆hfq for complementation completely restored impacted phenotypes. In addition, reverse transcription real-time quantitative PCR (RT-qPCR) analysis revealed that the expression of ten genes involved in bacterial growth and survival, motility and chemotaxis, and selenite or seleno-compound metabolism were influenced by Hfq loss-of-function by at least two-fold. Six genes including two involved in SeNPs production were positively regulated by hfq, while other four genes were negatively regulated. Homolog search suggested that the rprA gene might encode a small RNA regulated by Hfq in R. aquatilis HX2. Overall, the present study provides novel information about the function of Hfq and the regulation of bacterial biosynthesis of SeNPs.

    更新日期:2020-01-08
  • Yeast a potential bio-agent: future for plant growth and postharvest disease management for sustainable agriculture
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-08
    Arpan Mukherjee, Jay Prakash Verma, Anand Kumar Gaurav, Gowardhan Kumar Chouhan, Jai Singh Patel, Abd El-Latif Hesham

    Abstract The native microbial flora and fauna are replaced by commercial chemical fertilizers and pesticides, in the current agricultural system. Imbalance of beneficial microbial diversity and natural competitors increases the severity of plant diseases. Hence, sustainable agricultural practices like bio-inoculant, stress tolerant consortium, crop rotation and mix cropping sequences is only the solution of recharging the microbial population in soils to make healthier for crop productivity and suppression of soil borne phytopathogen. Microorganisms use several direct mechanism activities, e.g. production of plant hormones (indole-3-acetic acid), ammonium, siderophore and nutrient solubilization, and indirect mechanism activities, e.g. hydrogen cyanide, chitinase, protease and antibiotic for plant growth promotion. The plant growth-promoting effect of bacteria, fungi, mycorrhizal fungi and algae is widely explored. Yeast is a single-celled microbe classified as members of the kingdom fungi. Yeast and their product use in the food industry, medical science and biotechnological research purpose but very few literatures reported that yeasts have the ability to produce a group of plant growth-promoting activities and biocontrolling activity. Therefore, the main aim of this mini review is to highlight the application of yeasts as biological agents in different sectors of sustainable farming practices.

    更新日期:2020-01-08
  • Characterization of a cell density-dependent sRNA, Qrr, and its roles in the regulation of the quorum sensing and metabolism in Vibrio alginolyticus
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-06
    Huan Liu, Wang Liu, Xiaoxian He, Xuefeng Chen, Jinfang Yang, Yi Wang, Yue Li, Jiamin Ren, Wensheng Xu, Yanni Zhao

    Vibrio alginolyticus is an important fish pathogen causing pandemic diseases in marine animals. Small noncoding RNAs (sRNAs) are important posttranscriptional modulators of gene expression and involved in the pathogenesis of bacterial pathogens. Thus far, no cell density-dependent sRNA has been reported in V. alginolyticus. In this study, a cell density-dependent sRNA, Qrr, predicted based on the previous RNA-Seq analysis of V. alginolyticus cultured at low cell density (LCD) and high cell density (HCD), was characterized. The Qrr mutant showed significantly impaired growth and decreased swimming and swarming ability, and increased biofilm formation, extracellular polysaccharide content, serine protease production, and LD50 values during zebrafish infection in contrast to the wild-type strain. Qrr modulates the master regulators LuxR and AphA in quorum sensing (QS) pathways possibly at the posttranscriptional level by base pairing with the 5′-untranslated regions (5′-UTRs). Meanwhile, both LuxR and AphA could directly bind to the promoter of qrr to activate or repress its transcription, respectively. Moreover, our unbiased metabolic approaches revealed that Qrr modulates a large quantity of metabolic and lipidomic pathways, including amino acids, purine and pyrimidine derivatives, tricarboxylic acid cycle (TCA cycle) intermediates, and lipids. Collectively, this work contributes to a systematic understanding of regulatory roles of the cell density-dependent sRNA, Qrr, in V. alginolyticus.

    更新日期:2020-01-06
  • Integrating nanoparticle quantification and statistical design of experiments for efficient HIV-1 virus-like particle production in High Five cells
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-06
    Eduard Puente-Massaguer, Martí Lecina, Francesc Gòdia

    The nature of enveloped virus-like particles (VLPs) has triggered high interest in their application to different research fields, including vaccine development. The baculovirus expression vector system (BEVS) has been used as an efficient platform for obtaining large amounts of these complex nanoparticles. To date, most of the studies dealing with VLP production by recombinant baculovirus infection utilize indirect detection or quantification techniques that hinder the appropriate characterization of the process and product. Here, we propose the application of cutting-edge quantification methodologies in combination with advanced statistical designs to exploit the full potential of the High Five/BEVS as a platform to produce HIV-1 Gag VLPs. The synergies between CCI, MOI, and TOH were studied using a response surface methodology approach on four different response functions: baculovirus infection, VLP production, VLP assembly, and VLP productivity. TOH and MOI proved to be the major influencing factors in contrast with previous reported data. Interestingly, a remarkable competition between Gag VLP production and non-assembled Gag was detected. Also, the use of nanoparticle tracking analysis and flow virometry revealed the existence of remarkable quantities of extracellular vesicles. The different responses of the study were combined to determine two global optimum conditions, one aiming to maximize the VLP titer (quantity) and the second aiming to find a compromise between VLP yield and the ratio of assembled VLPs (quality). This study provides a valuable approach to optimize VLP production and demonstrates that the High Five/BEVS can support mass production of Gag VLPs and potentially other complex nanoparticles.

    更新日期:2020-01-06
  • Efficient affinity-tagging of M13 phage capsid protein IX for immobilization of protein III-displayed oligopeptide probes on abiotic platforms
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-04
    Zhou Tong, Laura A. Silo-Suh, Anwar Kalalah, Paul Dawson, Bryan A. Chin, Sang-Jin Suh

    We developed a genetic approach to efficiently add an affinity tag to every copy of protein IX (pIX) of M13 filamentous bacteriophage in a population. Affinity-tagged phages can be immobilized on a surface in a uniform monolayer in order to position the pIII–displayed peptides or proteins for optimal interaction with ligands. The tagging consists of two major steps. First, gene IX (gIX) of M13 phage is mutated in Escherichia coli via genetic recombineering with the gIX::aacCI insertion allele. Second, a plasmid that co-produces the affinity-tagged pIX and native pVIII is transformed into the strain carrying the defective M13 gIX. This genetic complementation allows the formation of infective phage particles that carry a full complement (five copies per virion) of the affinity-tagged pIX. To demonstrate the efficacy of our method, we tagged a M13 derivative phage, M13KE, with Strep-tag II. In order to tag pIX with Strep-tag II, the phage genes for pIX and pVIII were cloned and expressed from pASG-IBA4 which contains the E. coli OmpA signal sequence and Strep-Tag II under control of the tetracycline promoter/operator system. We achieved the maximum phage production of 3 × 1011 pfu/ml when Strep-Tag II-pIX-pVIII fusion was induced with 10 ng/ml of anhydrotetracycline. The complete process of affinity tagging a phage probe takes less than 5 days and can be utilized to tag any M13 or fd pIII-displayed oligopeptide probes to improve their performance.

    更新日期:2020-01-04
  • Analysis of the alginate O-acetylation machinery in Pseudomonas aeruginosa
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-04
    Wankuson Chanasit, Zennia Jean C. Gonzaga, Bernd H. A. Rehm

    O-acetylation of alginate produced by the opportunistic human pathogen Pseudomonas aeruginosa significantly contributes to its pathogenesis. Three proteins, AlgI, AlgJ and AlgF have been implicated to form a complex and act together with AlgX for O-acetylation of alginate. AlgI was proposed to transfer the acetyl group across the cytoplasmic membrane, while periplasmic AlgJ was hypothesised to transfer the acetyl group to AlgX that acetylates alginate. To elucidate the proposed O-acetylation multiprotein complex, isogenic knockout mutants of algI, algJ and algF genes were generated in the constitutively alginate overproducing P. aeruginosa PDO300 to enable mutual stability studies. All knockout mutants were O-acetylation negative and complementation with the respective genes in cis or trans restored O-acetylation of alginate. Interestingly, only the AlgF deletion impaired alginate production suggesting a link to the alginate polymerisation/secretion multiprotein complex. Mutual stability experiments indicated that AlgI and AlgF interact independent of AlgJ as well as impact on stability of the alginate polymerisation/secretion multiprotein complex. Deletion of AlgJ did not destabilise AlgX and vice versa. When the alginate polymerase, Alg8, was absent, then AlgI and AlgF stability was strongly impaired supporting a link of the O-acetylation machinery with alginate polymerisation. Pull-down experiments suggested that AlgI interacts with AlgJ, while AlgF interacts with AlgJ and AlgI. Overall, these results suggested that AlgI-AlgJ-AlgF form a multiprotein complex linked via Alg8 to the envelope-spanning alginate polymerisation/secretion multiprotein complex to mediate O-acetylation of nascent alginate. Here, we provide the first insight on how the O-acetylation machinery is associated with alginate production.

    更新日期:2020-01-04
  • New insights into transport capability of sugars and its impact on growth from novel mutants of Escherichia coli
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-04
    Alma Alva, Andrea Sabido-Ramos, Adelfo Escalante, Francisco Bolívar

    Abstract The fast-growing capability of Escherichia coli strains used to produce industrially relevant metabolites relies on their capability to transport efficiently glucose or potential industrial feedstocks such as sucrose or xylose as carbon sources. E. coli imports extracellular glucose into the periplasmic space across the outer membrane porins: OmpC, OmpF, and LamB. As the internal membrane is an impermeable barrier for sugars, the cell employs several primary and secondary active transport systems, and the phosphoenolpyruvate (PEP)-sugar phosphotransferase (PTS) system for glucose transport. PTS:glucose is the preferred system by E. coli to transport and phosphorylate the periplasmic glucose; nevertheless, PTS imposes a strict metabolic control mechanism on the preferential consumption of glucose over other carbon sources in sugar mixtures such as glucose and xylose resulting from the hydrolysis of lignocellulosic biomass, by the carbon catabolite repression. In this contribution, we summarize the major sugar transport systems for glucose and disaccharide transport, the exhibited substrate plasticity, and their impact on the growth of E. coli, highlighting the relevance of PTS in the control of the expression of genes for the transport and catabolism of other sugars as xylose. We discuss the strategies developed by evolved mutants of E. coli during adaptive laboratory evolution experiments to overcome the nutritional stress condition imposed by inactivation of PTS as a strategy for the selection of fast-growing derivatives in glucose, xylose, or mixtures of glucose:xylose. This approach results in the recruitment of other primary and secondary active transporters, demonstrating relevant sugar plasticity in derivative-evolved mutants. Elucidation of the molecular and biochemical basis of sugar-transport substrate plasticity represents a consistent approach for sugar-transport system engineering for the design of efficient E. coli derivative strains with improved substrate assimilation for biotechnological purposes.

    更新日期:2020-01-04
  • Stress responses linked to antimicrobial resistance in Acinetobacter species
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    Bora Shin, Chulwoo Park, Woojun Park

    Abstract Since the last 20 years, bacteria of the genus Acinetobacter have been the leading cause of hospital-acquired infections. In addition to the ability of Acinetobacter species to acquire rapid antibiotic resistance, limited knowledge on the mechanisms of multidrug resistance to antibiotics limits the treatment options for such infections. Here, we present a review of cellular processes, including oxidative stress defense, energy metabolism, ppGpp signaling, toxin-antitoxin system, and quorum sensing network in Acinetobacter species and their roles in antimicrobial resistance. Although inhibition of stress responses is an attractive approach to the development of effective antimicrobial therapeutic agents, it is crucial to understand the mechanisms that cause antibiotic resistance in Acinetobacter species, as they are not as well studied as those in other pathogenic bacteria. RelA/SpoT has been shown to be involved in ppGpp synthesis in all 50 genomes of 35 Acinetobacter species. However, toxin-antitoxin (TA) systems are present in less than 30% of the 50 genomes (28/30% of SplT/A; 14/14% of HigB/A; 4/6% of HicA/B), except the RelE/B system (30/78%). These data suggested that ppGpp signaling is conserved in Acinetobacter species, but TA systems are not. This review describes our current knowledge on stress responses with respect to antibiotic resistance or tolerance in pathogenic and non-pathogenic Acinetobacter species.

    更新日期:2020-01-04
  • Activation of paulomycin production by exogenous γ -butyrolactone signaling molecules in Streptomyces albidoflavus J1074
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    Yuwei Zhang, Min Wang, Jun Tian, Jia Liu, Zhengyan Guo, Wei Tang, Yihua Chen

    Abstract The interspecies communication roles of γ-butyrolactones (GBLs) have been described for a long time but are still poorly understood. Herein, we analyzed more than 1000 Streptomyces strains and noticed a big quantitative gap between the strains with GBL biosynthetic genes and the strains with GBL receptor genes, which implies the wide-spread of GBLs as interspecies signals in Streptomyces and their great potential in the activation of silent natural product gene clusters. Streptomyces albidoflavus J1074, which has one GBL receptor gene but no GBL biosynthetic gene, was chosen as a target to study the possible interspecies communication roles of GBLs. At first, the GBL biosynthetic genes from Streptomyces coelicolor M145 were expressed in S. albidoflavus J1074, which enabled the S. albidoflavus strains to synthesize Streptomyces coelicolor butanolides (SCBs) and activated the production of paulomycins. Further studies showed that this activation process requires the participation of the GBL receptor gene XNR_4681. The results suggest that the expression of exogenous GBL biosynthetic genes can modulate the metabolisms of GBL non-producing strains, and this regulation role might be meaningful for silent gene cluster activation in Streptomyces. At final, we synthesized racemic-SCB2 and tried to simplify the activation process by adding SCB2 directly to S. albidoflavus J1074, which unfortunately failed to induce paulomycin production.

    更新日期:2020-01-04
  • Technically relevant enzymes and proteins produced by LAB suitable for industrial and biological activity
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    Israel García-Cano, Diana Rocha-Mendoza, Erica Kosmerl, Lin Zhang, Rafael Jiménez-Flores

    Lactic acid bacteria (LAB) are a unique subset of microorganisms that have co-evolved with humans since the beginning of agricultural practices and animal domestication and throughout our never-ending quest for food preservation, digestibility, and flavor enhancement. LAB have historically played a preponderant role in our foods. In this review, we focus on the enzymatic activities and current or potential applications of LAB in our lives. A description of each of the enzymatic systems in LAB is included. Glycosidases, which hydrolyze the most abundant food molecules and as sources of carbon, sustain the lives of organisms on Earth as well as ensure microbial innocuity by the production of lactic acid from the uniquely mammalian carbohydrate, lactose. Lipases and proteases or proteinases are of fundamental importance in food fermentations and in dairy foods for flavor development. Bacteriocins and peptidoglycan hydrolases are part of the enzymatic system of LAB that has evolved to make these bacteria fierce competitors in various microbiomes, which are highly important for the human gut. In this review, we also present an explanation on how the versatility of the genetics of LAB can adapt to the matrix where they are placed with the advantage of not having any toxicity to humans. The systematic study of LAB enzymes has allowed for some unique applications in foods and biopharmaceutical industries. Here, we summarize how different enzyme systems in LAB are classified, and thus, facilitate much-needed further studies to understand the fundamentals and translate them into applications to improve our lives.

    更新日期:2020-01-04
  • Antibodies generated against dextransucrase exhibit potential anticariostatic properties in Streptococcus mutans
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    Shabeer Ahmad Rather, Sukesh Chander Sharma, Akhtar Mahmood

    Streptococcus mutans is a common principal causative agent of dental caries. In this communication, we describe that the antibodies raised against purified dextransucrase effectively inhibited the growth of S. mutans. The purified enzyme showed 58-fold enrichment, 17.5% yield and a specific activity of 3.96 units/mg protein. Purified IgG fraction of the antibody showed significant affinity with the antigenic protein. Immunotritation of the enzyme with dextransucrase antibody showed a gradual increase in inhibition of dextransucrase activity. The growth of S. mutans was also inhibited by 85% in the presence of 28 μg of IgG fraction of the antibody. Antibodies also impaired glucosyltransferase activity (72.8%) and biofilm formation by 92.6% in S. mutans. Western blot analysis revealed no cross reactivity with the various tissues of mice, rat, rabbit and humans. Dot blot analysis showed little reactivity with Lactobacillus acidophilus and Staphylococcus aureus and there was no reactivity with other bacterial strains like Enterococcus faecalis, Escherichia coli and Salmonella typhimurium. These findings suggest that antibody raised against dextransucrase exhibit inhibitory effects on the growth of S. mutans and biofilm formation with no reactivity with various mammalian tissues, thus it could be an effective anticariogenic agent.

    更新日期:2020-01-04
  • Nanomaterials: new weapons in a crusade against phytopathogens
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    Jyutika M. Rajwade, R. G. Chikte, K. M. Paknikar

    Bacteria, fungi, viruses, and nematodes are the major causal agents of plant diseases. These phytopathogens are responsible for about 10–40% losses in productivity and quality of food crops and horticultural produce. Although eradication of pathogens is not possible, control of plant diseases has been an area of continuous improvement/research. Use of antimicrobials, bacteriophages, and biocontrol agents, natural and synthetic agrochemicals along with best farm management practices constitute integrated measures for disease control. However, the quest for new materials continues due to pesticide resistance in the pathogens, emergence of new serotypes, and accumulation of high quantities of agrochemical contaminants in the ecosystem and associated environmental hazards, specificity of biocontrol agents, succession of pathogens during the plant growth phase, etc. The emergence of “nanotechnology,” a multidisciplinary field of research, has provided a plethora of nanomaterials for potential applications in the agricultural sector. Control of plant diseases requires agents that reduce the pathogen to manageable levels, tools for early-stage detection of pathogen, and compounds that elicit immune response in the host plants. Nanomaterials have in fact been assessed for their utility in all these approaches for disease control. The present review discusses nanomaterials for controlling phytopathogens, nanomaterials in plant disease diagnostics, and nanomaterials as elicitors of the plant immune system. These nanomaterials thus represent new weapons in the fight against the phytopathogens. Recent studies indicate that nanomaterials will be a crucial component in the agroecosystem.

    更新日期:2020-01-04
  • A new high-yielding antimicrobial peptide NZX and its antibacterial activity against Staphylococcus hyicus in vitro/vivo
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    He Liu, Na Yang, Ruoyu Mao, Da Teng, Ya Hao, Xiumin Wang, Jianhua Wang

    Staphylococcus hyicus, considered as a leading pathogen of exudative epidermitis, is a serious threat to humans and animals. The emergency of bacterial resistance to antibiotics, especially in human and animal health fields, leads to an urgent need of exploration of new antimicrobial agents. In this study, NZX, a plectasin-derived peptide, was firstly expressed in Pichia pastoris X-33 and was purified by cation exchange chromatography, followed by detection of its antibacterial activity in vitro and in vivo. The results showed that the total secreted protein concentration in fermentation supernatant was up to 2820 mg/L (29 °C) after 120-h induction in a 5-L fermentor. The yield of NZX reached up to 965 mg/L with a purity of 92.6%. The recombinant expressed NZX had a strong antimicrobial activity, high stability, and low toxicity. The minimal inhibitory concentrations (MICs) of NZX and ceftriaxone (CRO) against Gram-positive bacteria were 0.46 to 0.91 μM and 6.04 to 12.09 μM, respectively. The time-killing curves showed that S. hyicus NCTC10350 was killed completely by 2× and 4 × MIC of NZX within 24 h. NZX also exhibited the intracellular activity against S. hyicus in Hacat cells. After treatment with NZX (10 mg/kg) and CRO (60 mg/kg), the survival rates of mice were 100% and 83.3%, respectively. NZX inhibited the bacterial translocation, downregulated pro-inflammatory cytokines (TNF-α/IL-1β/IL-6), upregulated the anti-inflammatory cytokine (IL-10), and ameliorated multiple-organ injuries (the liver, spleen, lung, and kidney). This study provides evidence that the expressed NZX has the potential to become a powerful candidate as novel antimicrobial agents against S. hyicus infections.

    更新日期:2020-01-04
  • A pH-responsive genetic sensor for the dynamic regulation of D-xylonic acid accumulation in Escherichia coli
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    Angelo B. Bañares, Kris Niño G. Valdehuesa, Kristine Rose M. Ramos, Grace M. Nisola, Won-Keun Lee, Wook-Jin Chung

    Abstract The xylose oxidative pathway (XOP) is continuously gaining prominence as an alternative for the traditional pentose assimilative pathways in prokaryotes. It begins with the oxidation of D-xylose to D-xylonic acid, which is further converted to α-ketoglutarate or pyruvate + glycolaldehyde through a series of enzyme reactions. The persistent drawback of XOP is the accumulation of D-xylonic acid intermediate that causes culture media acidification. This study addresses this issue through the development of a novel pH-responsive synthetic genetic controller that uses a modified transmembrane transcription factor called CadCΔ. This genetic circuit was tested for its ability to detect extracellular pH and to control the buildup of D-xylonic acid in the culture media. Results showed that the pH-responsive genetic sensor confers dynamic regulation of D-xylonic acid accumulation, which adjusts with the perturbation of culture media pH. This is the first report demonstrating the use of a pH-responsive transmembrane transcription factor as a transducer in a synthetic genetic circuit that was designed for XOP. This may serve as a benchmark for the development of other genetic controllers for similar pathways that involve acidic intermediates.

    更新日期:2020-01-04
  • Development and evaluation of a gp85 protein-based subgroup-specific indirect enzyme-linked immunosorbent assay for the detection of anti-subgroup J avian leukosis virus antibodies
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    Fangfang Chang, Lixiao Xing, Zhifeng Xing, Mengmeng Yu, Yuanling Bao, Suyan Wang, Muhammad Farooque, Xinyi Li, Peng Liu, Qing Pan, Xiaole Qi, Li Gao, Kai Li, Changjun Liu, Yanping Zhang, Hongyu Cui, Xiaomei Wang, Yulong Gao

    Abstract Avian leukosis virus subgroup J (ALV-J) is an important pathogen for various neoplasms and causes significant economic losses in the poultry industry. Serological detection of specific antibodies against ALV-J infection is important for successful clinical diagnosis. Here, a 293F stable cell line was established to stably express gp85 protein. In this cell line, gp85 protein was expressed at approximately 30 mg/L. A subgroup-specific indirect enzyme-linked immunosorbent assay (iELISA) was developed using ALV-J gp85 protein as coated antigen to detect antibodies against ALV-J. The sensitivity of the iELISA (1:51200 diluted in serum) was 16 times more than that of indirect immunofluorescence assay (IFA; 1:3200 diluted in serum). Moreover, there was no crossreactivity with antibodies against other common avian viruses and other avian leukosis virus subgroups, such as subgroups A and B. The practicality of the iELISA was further evaluated by experimental infection and clinical samples. The results from experimental infection indicated that anti-ALV-J antibodies were readily detected by iELISA as early as 4 weeks after ALV-J infection, and positive antibodies were detected until 20 weeks, with an antibody-positive rate of 11.1% to 33.3%. Moreover, analysis of clinical samples showed that 9.49% of samples were positive for anti-ALV-J antibodies, and the concordance rate of iELISA and IFA was 99.24%. Overall, these results suggested that the subgroup-specific iELISA developed in this study had good sensitivity, specificity, and feasibility. This iELISA will be very useful for epidemiological surveillance, diagnosis, and eradication of ALV-J in poultry farms.

    更新日期:2020-01-04
  • Construction and characterization of a chimeric lysin ClyV with improved bactericidal activity against Streptococcus agalactiae in vitro and in vivo
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    Li Huang, Dehua Luo, Vijay S. Gondil, Yujing Gong, Minghui Jia, Dazhong Yan, Jin He, Shencai Hu, Hang Yang, Hongping Wei

    Abstract The emergence of antibiotic-resistant beta-hemolytic Streptococcus agalactiae strains poses increasing threat to human beings globally. As an attempt to create a novel lysin with improved activity against S. agalactiae, a chimeric lysin, ClyV, was constructed by fusing the enzymatically active domain (EAD) from PlyGBS lysin (GBS180) and the cell wall binding domain (CBD) from PlyV12 lysin (V12CBD). Plate lysis assay combined with lytic kinetic analysis demonstrated that ClyV has improved activity than its parental enzymatic domain GBS180 against multiple streptococci. Biochemical characterization showed that ClyV is active from pH 7 to 10, with the optimum pH of 9, and is stable under NaCl concentration of < 500 mM. In a S. agalactiae infection model, a single intraperitoneally administration of 0.1 mg/mouse of ClyV protected 100% mice, while it was observed that ~ 29% survive in group that received a single dose of 0.1 mg/mouse of GBS180. Moreover, a high dose of 0.8 mg/mouse ClyV did not show any adverse effects to the health or survival rate of the mice. Considering the robust bactericidal activity and good safety profile of ClyV, it represents a potential candidate for the treatment of S. agalactiae infections.

    更新日期:2020-01-04
  • Engineering viable foot-and-mouth disease viruses with increased acid stability facilitate the development of improved vaccines
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    Hong Yuan, Pinghua Li, Huifang Bao, Pu Sun, Xingwen Bai, Qifeng Bai, Na Li, Xueqing Ma, Yimei Cao, Yuanfang Fu, Kun Li, Jing Zhang, Dong Li, Yingli Chen, Jie Zhang, Zengjun Lu, Zaixin Liu

    Foot-and-mouth disease virus (FMDV), the most acid-unstable virus among picornaviruses, tends to disassemble into pentamers at pH values slightly below neutrality. However, the structural integrity of intact virion is one of the most important factors that influence the induction of a protective antibody response. Thus, improving the acid stability of FMDV is required for the efficacy of vaccine preparations. According to the previous studies, a single substitution or double amino acid substitutions (VP1 N17D, VP2 H145Y, VP2 D86H, VP3 H142D, VP3 H142G, and VP1 N17D + VP2 H145Y) in the capsid were introduced into the full-length infectious clone of type O FMDV vaccine strain O/HN/CHN/93 to develop seed FMDV with improved acid stability. After the transfection into BSR/T7 cells of constructed plasmids, substitution VP1 N17D or VP2 D86H resulted in viable and genetically stable FMDVs, respectively. However, substitution VP2 H145Y or VP1 N17D + VP2 H145Y showed reverse mutation and additional mutations, and substitution VP3 H141G or VP3 H141D prevented viral viability. We found that substitution VP1 N17D or VP2 D86H could confer increased acid resistance, alkali stability, and thermostability on FMDV O/HN/CHN/93, whereas substitution VP1 N17D was observed to lead to a decreased replication ability in BHK-21 cells and mildly impaired virulence in suckling mice. In contrast, substitution VP2 D86H had no negative effect on viral infectivity. These results indicated that the mutant rD86H carrying substitution VP2 D86H firstly reported by us could be more adequate for the development of inactivated FMD vaccines with enhanced acid stability.

    更新日期:2020-01-04
  • Penicillin and cephalosporin biosyntheses are also regulated by reactive oxygen species
    Appl. Microbiol. Biotechnol. (IF 3.670) Pub Date : 2020-01-03
    María Esmeralda Bibián, Ailed Pérez-Sánchez, Armando Mejía, Javier Barrios-González

    Abstract In an earlier work on lovastatin production by Aspergillus terreus, we found that reactive oxygen species (ROS) concentration increased to high levels precisely at the start of the production phase (idiophase) and that these levels were sustained during all idiophase. Moreover, it was shown that ROS regulate lovastatin biosynthesis. ROS regulation has also been reported for aflatoxins. It has been suggested that, due to their antioxidant activity, aflatoxins are regulated and synthesized like a second line of defense against oxidative stress. To study the possible ROS regulation of other industrially important secondary metabolites, we analyzed the relationship between ROS and penicillin biosynthesis by Penicillium chrysogenum and cephalosporin biosynthesis by Acremonium chrysogenum. Results revealed a similar ROS accumulation in idiophase in penicillin and cephalosporin fermentations. Moreover, when intracellular ROS concentrations were decreased by the addition of antioxidants to the cultures, penicillin and cephalosporin production were drastically reduced. When intracellular ROS were increased by the addition of exogenous ROS (H2O2) to the cultures, proportional increments in penicillin and cephalosporin biosyntheses were obtained. It was also shown that lovastatin, penicillin, and cephalosporin are not antioxidants. Taken together, our results provide evidence that ROS regulation is a general mechanism controlling secondary metabolism in fungi.

    更新日期:2020-01-04
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