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  • Metabolite profiling reveals a complex response of plants to application of plant growth-promoting endophytic bacteria
    Microbiol. Res. (IF 3.701) Pub Date : 2020-01-25
    Ahmad Mahmood; Ryota Kataoka

    Endophytic bacteria have been explored for their role in plant growth promotion, however, not much has been explored in cucumber. The metabolomic response of plants to application of such microbes also remains largely unknown. Thus, we investigated the application of endophytic bacteria to cucumber to infer their role in plant growth promotion and document metabolome response. The lowest healthy leaf-stalks were sampled from four differently sourced cucumber plants, and endophytic bacteria were isolated after surface disinfection. Initial plant growth-promoting (PGP) screening was performed to identify PGP strains out of numerous isolates, and five strains (Strains 4=Curtobacterium spp., 72=Brevibacillus spp., 167=Paenibacillus spp., 193=Bacillus spp., and 227=Microbacterium spp.) were selected based on their contribution to root growth compared with the control. The selected strains were further evaluated in pot experiments, axenic PGP trait assays, and metabolomic analysis. Results revealed that the selected isolates possessed different qualitative characteristics among indole acetic acid, siderophore production, phosphate solubilization, and 1-aminocyclopropane-1-carboxylate (ACC)-deaminase and nifH genes, and all isolates significantly enhanced plant growth in both pot experiments compared with the uninoculated control and fertilizer control. Metabolomic profiling revealed that both strains affected the plant metabolomes compared with the uninoculated control. Around 50% of the metabolites explored had higher concentrations in either or both bacteria-applied plants compared with the uninoculated control. Differences were observed in both strains’ regulation of metabolites, although both enhanced root growth near equally. Overall, endophytic bacteria significantly enhanced plant growth and tended to produce or induce release of certain metabolites within the plant endosphere.

    更新日期:2020-01-26
  • Induction of drought tolerance in tomato upon the application of ACC deaminase producing plant growth promoting rhizobacterium Bacillus subtilis Rhizo SF 48
    Microbiol. Res. (IF 3.701) Pub Date : 2020-01-25
    H.G. Gowtham; S. Brijesh Singh; M. Murali; N. Shilpa; Melvin Prasad; Mohammed Aiyaz; K.N. Amruthesh; S.R. Niranjana

    A total of ten 1-aminocyclopropane-1-carboxylate (ACC) deaminase producing PGPR isolates were selected and evaluated for the induction of drought stress tolerance in tomato. Among the selected PGPR, maximum seed (laboratory) and plant growth promotion (greenhouse) was observed in tomato seeds bacterized with Bacillus subtilis Rhizo SF 48. The genomic study confirmed the presence of ACC deaminase gene in Rhizo SF 48 and the obtained sequence was deposited to the NCBI database with the Accession No. MK652706. The tomato plants grown upon treatment with Rhizo SF 48 significantly enhanced plant growth even after exposing to different levels of drought stress as compared to stress induced control plants. About 7.5% and 38% increase in RWC were observed in Rhizo SF 48 treated tomato plants grown under well-watered and stress conditions (S4) compared to their control plants, respectively. An increase of 0.76, 0.23 and 0.78 fold in proline, SOD and APX activity and a decrease of 0.3 fold in MDA and H2O2 contents were observed in Rhizo SF 48 treated plants compared to control plants grown under S4 conditions. The histo-chemical studies showed lower accumulations of H2O2 and superoxide anion in the leaves of Rhizo SF 48 treated plants under drought stress, which was in confirmation with the quantification results of H2O2 and SOD. The qRT-PCR studies on drought (Le25) and ethylene responsive factor (SlERF84) marker genes showed that a significant decrease of 0.75 and 0.81 folds, respectively in Le25 and SlERF84 accumulation was observed in Rhizo SF 48 treated plants compared to untreated plants grown under S4 conditions. From the results, it can be attributed that ACC deaminase producing Rhizo SF 48 was able to protect tomato plants against oxidative damage caused due to drought stress and enhanced plant growth promotion. It can be concluded that ACC deaminase producing Rhizo SF 48 can serve as a useful bio-inoculant for sustainable tomato production in arid and semi-arid regions with water deficit.

    更新日期:2020-01-26
  • Shotgun Proteomic Analysis of ESBL-Producing and Non-ESBL-Producing Klebsiella Pneumoniae Clinical Isolates
    Microbiol. Res. (IF 3.701) Pub Date : 2020-01-25
    Shymaa Enany; Samira Zakeer; Ahmed A. Sayed

    Klebsiella pneumoniae is a pathogenic bacterium that is responsible for a wide range of infections in humans. An increased rate of infections caused by multi-drug-resistant K. pneumoniae has been noted in the last two decades. The association between antimicrobial resistance and virulence is an important topic of study. Genomic tools have been used widely for the detection of virulence. In our study, we used proteomic analysis with mass spectrometry and bioinformatics tools to explore the virulence factors of both ESBL-producing and non-ESBL-producing K. pneumoniae and to determine the association between virulence and antimicrobial resistance in these clinical isolates. We have revealed different proteomic profiles and different pathways between the ESBL- and non-ESBL-producing groups. Many proteins involved in stress responses have been reported in the shared proteome between ESBL-and non-ESBL producers, such as ElaB protein, Lon protease, and universal stress proteins G and A. The virulence and pathogenicity of ESBL-producing bacteria were stronger than those of the non-ESBL-producing bacteria. Several unique virulence determinants were identified in ESBL-producing K. pneumoniae, such as proteins with lyase, catalase, isochorismatase, and oxidoreductase activity.

    更新日期:2020-01-26
  • Diversity of endophytic plant-growth microorganisms from Gentianella weberbaueri and Valeriana pycnantha, highland Peruvian medicinal plants
    Microbiol. Res. (IF 3.701) Pub Date : 2020-01-15
    Rocío Ulloa-Muñoz; Percy Olivera-Gonzales; Alberto Castañeda-Barreto; Gretty K. Villena; Carmen Tamariz-Angeles

    Microbial diversity in Peruvian mountain areas is poorly know, specially endophytic microorganisms of medicinal native plants from the Cordillera Blanca. So, nine bacterial and six fungal species were isolated from Gentianella weberbaueri and Valeriana pycnantha. According to 16S rDNA analysis, bacterial strains belong to genera Rahnella, Pseudomonas, Serratia, Rouxiella, and Bacillus; while ITS analysis showed that fungi belong to Pyrenochaeta, Scleroconidioma, Cryptococcus, and Plenodomus genera. Rahnella sp. GT24B and P. trivialis VT20B solubilized tricalcium phosphate and produced siderophores at 10 and 24 °C. Five bacteria strains produced indol-3-acetic acid (IAA) at 10 and 24 °C, where Rahnella sp. VT19B showed more production at 10 °C than 24 °C. Rahnella sp. GT24B, Serratia sp. VT28B, and Rahnella sp. GT25B inhibited Fusarium oxysporum growth up to 100, 78 and 74%, respectively. R. inusitata VT25B and B. licheniformis GT10B showed high cellulolytic and proteolytic activities. On the other hand, only a few fungi moderately inhibited growth of F. oxysporum, and produced siderophores and cellulases. Most of bacteria inoculated on Medicago sativa “alfalfa” and Triticum aestivum “wheat” seeds got better root development, especially Rahnella sp. GT24B, Rouxiella sp.VT24B, Serratia sp. VT28B, and Rahnella sp. VT34B. Finally, this study is the first report of endophytic microorganisms associated to wild medicinal high-mountain Peruvian plants and it show a valuable microbial diversity and its possible role in promoting growth of crops and wild medicinal plants.

    更新日期:2020-01-15
  • Pantoea Natural Product 3 is encoded by an eight-gene biosynthetic gene cluster and exhibits antimicrobial activity against multi-drug resistant Acinetobacter baumannii and Pseudomonas aeruginosa
    Microbiol. Res. (IF 3.701) Pub Date : 2020-01-15
    Ashley N. Williams; John Stavrinides

    Multi-drug resistant Acinetobacter baumannii and Pseudomonas aeruginosa continue to pose a serious health threat worldwide. Two Pantoea agglomerans strains, 3581 and SN01080, produce an antibiotic effective against these pathogens. To identify the antibiotic biosynthetic gene clusters, independent genetic screens were conducted for each strain using a mini-Tn5 transposon, which resulted in the identification of the same conserved eight-gene cluster. We have named this antibiotic Pantoea Natural Product 3 (PNP-3). The PNP-3 biosynthetic cluster is composed of genes encoding two Major Facilitator Superfamily (MFS) transporters, an ArsR family regulator, and five predicted enzymes. The biosynthetic gene cluster is found in only a few Pantoea strains and is not present within the antiSMASH and BAGEL4 databases, suggesting it may be novel. In strain 3581, PNP-3 production is linked to pantocin A production, where loss of pantocin A production results in a larger PNP-3 zone of inhibition. To evaluate the spectrum of activity, PNP-3 producers, including several PNP-3 mutants and pantocin A site-directed mutants, were tested against a collection of clinical, drug-resistant strains of A. baumannii and P. aeruginosa, as well as, Klebsiella, Escherichia coli, Enterobacter, Staphylococcus aureus, and Streptococcus mutans. PNP-3 was found to be effective against all strains except vancomycin-resistant Enterococcus under the tested conditions. Heterologous expression of the four predicted biosynthetic genes in Erwinia amylovora resulted in antibiotic production, providing a means for future overexpression and purification. PNP-3 is a natural product that is effective against drug-resistant A. baumannii, P. aeruginosa, and enteric species for which there are currently few treatment options.

    更新日期:2020-01-15
  • Genotyping and population diversity of Bacillus anthracis in China based on MLVA and canSNP analysis
    Microbiol. Res. (IF 3.701) Pub Date : 2020-01-15
    Dongshu Wang; Bingxiang Wang; Li Zhu; Songyu Wu; Yufei Lyu; Erling Feng; Chao Pan; Lei Jiao; Yujun Cui; Xiankai Liu; Hengliang Wang

    In pastoral parts of China, anthrax still presents a major risk to livestock and threatens the health of local human populations. Currently, whole-genome-based molecular markers, such as single-nucleotide polymorphisms (SNPs) and variable number tandem repeats (VNTRs), are the most effective tools for genotyping Bacillus anthracis. In this study, 191 isolates were selected to assess the diversity of B. anthracis in China. Five isolates were confirmed not to be B. anthracis by clustered regularly interspaced short palindromic repeat analysis, while the remaining 186 isolates were typed using canonical SNP (canSNP) and VNTR analyses. Five sublineages/subgroups, A.Br.001/002, A.Br.Vollum, A.Br.Aust.94, A.Br.Ames, and A.Br.008/009, were detected based on 13 canSNP sites. The 186 isolates were further assigned 114 sequence types based on 27 VNTR loci, with major branches correlating with the canSNP analysis. We then used a simplified multiple-locus variable number tandem repeat analysis (MLVA) protocol (MLVAmin) based on eight high-resolution VNTR sites to analyze the Chinese isolates, with the resulting phylogeny again agreeing with the canSNP analysis. We also developed two schemes, MLVAc and MLVAp, using various numbers of VNTRs to analyze different canSNP sublineages to increase the typing resolution of the canSNP protocol. The results showed a highly imbalanced geographical distribution of the B. anthracis population, with four different sublineages observed in Xinjiang Province, while only one sublineage, A.Br.001/002, was found in the other six provinces, except for three A.Br.Ames strains isolated from Inner Mongolia. Based on the MLVA and canSNP analysis, the spread of B. anthracis appears to have occurred from west to east via three independent routes.

    更新日期:2020-01-15
  • The orphan histidine kinase PdtaS-p regulates both morphological differentiation and antibiotic biosynthesis together with the orphan response regulator PdtaR-p in Streptomyces
    Microbiol. Res. (IF 3.701) Pub Date : 2020-01-14
    Lei Li; Yawei Zhao; Jingjing Ma; Hengnuo Tao; Guosong Zheng; Jun Chen; Weihong Jiang; Yinhua Lu

    In Streptomyces pristinaespiralis, the orphan histidine kinase (HK) PdtaS-p (encoded by SSDG_02492), which belongs to proteins of two-component systems (TCSs), plays an important role in both morphological differentiation and antibiotic biosynthesis. Owing to the isolated genetic organization of pdtaS-p, it is a challenge to identify its cognate response regulator (RR) and hampers the efforts to elucidate the regulation mechanism of PdtaS-p. In this study, based on bioinformatics analysis, we identify the cognate RR PdtaR-p of PdtaS-p by phenotype similarity of gene deletion mutants as well as in vitro phosphor-transfer assay. We show that the mutants (ΔpdtaR-p and ΔpdtaS-p) exhibit almost the same phenotypical changes, showing a bald phenotype on MS agar and reduced pristinamycin biosynthesis. Further phosphor-transfer assay indicates that the phosphoryl group of HK PdtaS-p can be specifically transferred to RR PdtaR-p. Compared with the majority of RRs that harbor DNA-binding domains, PdtaR-p contains a putative ANTAR RNA-binding domain involved in controlling gene expression at the post-transcription level. Finally, we demonstrate that their ortholog from the model strain Streptomyces coelicolor, PdtaS-c/PdtaR-c, also regulates both morphological differentiation and antibiotics biosynthesis, suggesting that PdtaS-p/PdtaR-p-mediated molecular regulation may be conserved in the genus Streptomyces. To our knowledge, this is the first report describing the functional identification of ANTAR RNA-binding regulators in Streptomyces.

    更新日期:2020-01-14
  • Genomic and Phenomic Analysis of a Marine Bacterium, Photobacterium marinum J15
    Microbiol. Res. (IF 3.701) Pub Date : 2020-01-09
    Noordiyanah Nadhirah Roslan; Mohamad Syazwan Ngalimat; Adam Thean Chor Leow; Siti Nurbaya Oslan; Syarul Nataqain Baharum; Suriana Sabri

    Photobacterium species are widely distributed in the marine environment. The overall metabolism of this genus remains largely unknown. In order to improve our knowledge on this bacterium, the relationship between the genome and phenome of the Photobacterium isolate was analyzed. The cream colored, Gram-negative, rod-shaped and motile bacterial strain, J15, was isolated from marine water of Tanjung Pelepas, Johor, Malaysia. The 5,684,538 bp genome of strain J15 comprised 3 contigs (2 chromosomes and 1 plasmid) with G + C content of 46.39 % and contained 4,924 protein-coding genes including 180 tRNAs and 40 rRNAs. The phenotypic microarray (PM) as analyzed using BIOLOG showed the utilization of; i) 93 of the 190 carbon sources tested, where 61 compounds were used efficiently; ii) 41 of the 95 nitrogen sources tested, where 22 compounds were used efficiently; and iii) 3 of the 94 phosphorous and sulphur sources tested. Furthermore, high tolerance to osmotic stress, basic pH and toxic compounds as well as resistance to antibiotics of strain J15 were determined by BIOLOG PM. The ANI and kSNP analyses revealed that strain J15 to be the same species with Photobacterium marinum AK15 with ANI value of 96.93 % and bootstrapping value of 100 in kSNP. Based on the ANI and kSNP analyses, strain J15 was identified as P. marinum J15.

    更新日期:2020-01-09
  • Beneficial effect of GABA-rich fermented milk on insomnia involving regulation of gut microbiota
    Microbiol. Res. (IF 3.701) Pub Date : 2020-01-07
    Leilei Yu; Xiao Han; Shi Cen; Hui Duan; Saisai Feng; Yuzheng Xue; Fengwei Tian; Jianxin Zhao; Hao Zhang; Qixiao Zhai; Wei Chen
    更新日期:2020-01-07
  • Revealing the impact of global mass bleaching on coral microbiome through 16S rRNA gene-based metagenomic analysis
    Microbiol. Res. (IF 3.701) Pub Date : 2019-12-31
    Ramu Meenatchi; Thangadurai Thinesh; Pownraj Brindangnanam; Saqib Hassan; George Seghal Kiran; Joseph Selvin

    Coral bleaching, a phenomenon by which the expulsion of corals’ alveolate endosymbiont (zooxanthellae) occurs when experiencing thermal stress is the major cause for devastation of corals. However, apart from this obligate symbiont of Scleractinian corals, there are different kinds of microbes that exist as stable, transient or sporadic members of the holobiont which resides within various microhabitats in the coral structures. Thus, this study aims to profile the coral bacterial community composition among different coral genera (thermally-sensitive (Acropora digetifera and A. noblis) and thermally resistant (Favites abdita) coral genera analyzed by field monitoring surveys) and also in a particular coral genus (thermally sensitive coral-A. digetifera) at two different sampling times (March 2016 and January 2017). A total of about 608695 paired end reads were obtained through Illumina MiSeq Sequencing platform. The alpha diversity indices (ACE, Chao1 and Shannon) were found to be higher in A. nobilis, followed by A. digetifera and Favites abdita, and the corresponding Simpson values were also found to follow the same trend, showing the sample are both rich in species diversity and species evenness. Proteobacteria was found to be the most dominant phylum and Gammaproteobacteria was the predominant class present in all the coral genera studied as well as at different sampling time periods. As Vibrionaceae was previously reported to increase its abundance during bleaching stress conditions, bacteria profiling among different coral genera showed the presence of 86% Vibrionaceae in A. digetifera colonies, and it was 93% in A. digetifera samples collected during March 2016 whereas, it was found to decrease significantly (7%) in same tagged colonies collected during January 2017. Thus, profiling of microbiome is of prime importance while studying the holobiont organism like the corals. Stress level experienced by Palk Bay are even depicted in this microbiome study showing high alpha diversity indices alarms the reef managers to get attention over this precious stress tolerant reef community.

    更新日期:2019-12-31
  • Bacterial line of defense in Dirinaria lichen from two different ecosystems: First genomic insights of its mycobiont Diriniria sp. GBRC AP01
    Microbiol. Res. (IF 3.701) Pub Date : 2019-12-28
    Apurvasinh C. Puvar; Neelam M. Nathani; Inayatullah Shaikh; Arpan D. Bhatt; Poonam Bhargava; Chaitanya G. Joshi; Madhvi N. Joshi

    Lichens have been widely studied for their symbiotic properties and for the secondary metabolites production by its fungal symbiont. Recent molecular studies have confirmed coexistence of bacteria along with the fungal and algal symbionts. Direct nucleic acid study by -omics approaches is providing better insights into their structural and functional dynamics. However, genomic analysis of individual members of lichen is difficult by the conventional approach. Hence, genome assembly from metagenome data needs standardization in the eukaryotic system like lichens. The present study aimed at metagenomic characterization of rock associated lichen Dirinaria collected from Kutch and Dang regions of Gujarat, followed by genome reconstruction and annotation of the mycobiont Dirinaria. The regions considered in the study are eco-geographically highly variant. The results revealed higher alpha diversity in the dry region Kutch as compared to the tropical forest associated lichen from Dang. Ascomycota was the most abundant eukaryote while Proteobacteria dominated the bacterial population. There were 23 genera observed only in the Kutch lichen (KL) and one genus viz., Candidatus Vecturithrix unique to the Dang lichen (DL). The exclusive bacterial genera in the Kutch mostly belonged to groups reported for stress tolerance and earlier isolated from lithobionts of extreme niches. The assembled data of KL & DL were further used for genome reconstruction of Dirinaria sp. using GC and tetra-pentamer parameters and reassembly that resulted into a final draft genome of 31.7 Mb and 9556 predicted genes. Twenty-eight biosynthesis gene clusters were predicted that included genes for polyketide, indole and terpene synthesis. Association analysis of bacteria and mycobiont revealed 8 pathways specific to bacteria with implications in lichen symbiosis and environment interaction. The study provides the first draft genome of the entire fungal Dirinaria genus and provides insights into the Dirinaria lichen metagenome from Gujarat region.

    更新日期:2019-12-29
  • Selected isolates of Trichoderma gamsii induce different pathways of systemic resistance in maize upon Fusarium verticillioides challenge
    Microbiol. Res. (IF 3.701) Pub Date : 2019-12-19
    Stefania Galletti; Roberta Paris; Stefano Cianchetta

    The pink ear rot is one of the most damaging maize diseases, caused by the mycotoxigenic fungal pathogen, Fusarium verticillioides. The application of biological control agents, like antagonistic and/or resistance inducer microorganisms, is an option to reduce fungal infection and kernel contamination in a sustainable and environmentally friendly way. It is well known that Trichoderma species are non-pathogenic fungi able to antagonize plant pathogens and to induce systemic resistance in plants. The present work aimed to verify if Trichoderma spp., applied to maize kernels, affect the plant growth and induce systemic responses to F. verticillioides. Besides, the capability to reduce fumonisin concentration in liquid cultures was investigated. Two T. gamsii (IMO5 and B21), and one T. afroharzianum (B75) isolates, selected both for antagonism and for the ability to reduce root infections, significantly reduced the endophytic development of the stem-inoculated pathogen, compared to the control. The mechanisms of action appeared to be strain-specific, with IMO5 enhancing transcript levels of marker genes of Induced Systemic Resistance (ZmLOX10, ZmAOS, and ZmHPL) while B21 enhancing marker genes of Systemic Acquired Resistance (ZmPR1 and ZmPR5), as evinced by measuring their expression profiles in the leaves. Moreover, IMO5 promoted plant growth, while B21 was able to significantly reduce the fumonisin content in a liquid medium. The results of this work give new evidence that the seed application of T. gamsii is a promising tool for controlling F. verticillioides to be integrated with breeding and the adoption of good agricultural practices.

    更新日期:2019-12-19
  • Isolation and characterization of psychrophilic and psychrotolerant plant-growth promoting microorganisms from a high-altitude volcano crater in Mexico
    Microbiol. Res. (IF 3.701) Pub Date : 2019-12-14
    Irán Tapia Vázquez; Ricardo Sánchez; Marisol Arroyo; Verónica Lira-Ruan; Ayixón Sánchez-Reyes; María del Rayo Sánchez-Carbente; Daniel Padilla-Chacón; Ramón Alberto Batista-García; Jorge Luis Folch-Mallol

    Extreme ecosystems are a possible source of new interesting microorganisms, in this study the isolation of psychrophilic and psychrotolerant plant growth promoting microorganisms was pursued in a cold habitat, with the aim of finding novel microbes that can protect crops from cold. Eight yeast and four bacterial strains were isolated from rhizospheric soil collected from the Xinantécatl volcano in Mexico, and characterized for plant growth promoting properties. Most of the yeasts produced indole acetic acid and hydrolytic enzymes (cellulases, xilanases and chitinases), but none of them produced siderophores, in contrast to their bacterial counterparts. Inorganic phosphate solubilization was detected for all the bacterial strains and for two yeast strains. Yeast and bacterial strains may inhibit growth of various pathogenic fungi, propounding a role in biological control. Microorganisms were identified up to genera level, by applying ribotyping techniques and phylogenetic analysis. Bacterial strains belonged to the genus Pseudomonas, whereas yeast strains consisted of Rhodotorula sp. (4), Mrakia sp. (3) and Naganishia sp. (1). New species belonging to the aforementioned genera seem to have been isolated from both bacteria and yeasts. Germination promoting activity on Solanum lycopersicum seeds was detected for all strains compared to a control, whereas tomato plantlets, grown at 15 °C in the presence of some of the strains, performed better than the non-inoculated plantlets. This study offers the possibility of using these strains as an additive to improve culture conditions of S. lycopersicum in a more environmentally compatible way. This is the first study to propose psychrophilic/psychrotolerant yeasts, as plant growth promoting microbes.

    更新日期:2019-12-17
  • Isolation and characterization of Burkholderia cenocepacia CR318, a phosphate solubilizing bacterium promoting corn growth
    Microbiol. Res. (IF 3.701) Pub Date : 2019-12-14
    Man You; Shumei Fang; Jacqueline MacDonald; Jianping Xu; Ze-Chun Yuan

    Plant-growth promoting rhizobacteria benefit crop health and growth through various mechanisms including phosphate and potassium solubilisation, and antimicrobial activity. Previously, we sequenced the genome of bacterial strain Burkholderia cenocepacia CR318, which was isolated from the roots of the starch corn (Zea mays L.) in London, Ontario, Canada. In this work, the species identity of this isolate is confirmed by recA phylogeny and in silico DNA-DNA hybridization (isDDH), and its plant-growth promoting characteristics are described. B. cenocepacia CR318 exhibited strong activity of inorganic phosphate and potassium solubilization. It significantly promoted the growth of corn plants and roots by solubilizing inorganic tricalcium phosphate under greenhouse conditions. Functional analysis of the complete B. cenocepacia CR318 genome revealed genes associated with phosphate metabolism such as pstSCAB encoding a high affinity inorganic phosphate-specific transporter, and the pqqABCDE gene cluster involved in the biosynthesis of pyrroloquinoline quinone (PQQ), which is a required cofactor for quinoprotein glucose dehydrogenase (Gdh). However, it appears that B. cenocepacia CR318 lacks the quinoprotein Gdh which can produce gluconic acid to solubilize inorganic phosphate. Overall, these findings provide an important step in understanding the molecular mechanisms underlying the plant growth promotion trait of B. cenocepacia CR318.

    更新日期:2019-12-17
  • Isolation of bacteria at different points of Pleurotus ostreatus cultivation and their influence in mycelial growth
    Microbiol. Res. (IF 3.701) Pub Date : 2019-12-13
    Christian Suarez; Stefan Ratering; Victoria Weigel; Julia Sacharow; Jackeline Bienhaus; Janine Ebert; Anika Hirz; Martin Rühl; Sylvia Schnell

    Pleurotus ostreatus is one of the most cultivated edible mushrooms worldwide and few approaches have been done to analyze bacterial influence during its cultivation. Therefore, bacteria from commercial spawn, mycelial-colonized straw and fruiting bodies from healthy productive samples were counted, isolated and tested for their mycelial growth promoting ability. Bacterial cell numbers at different steps of the process showed low bacterial cell numbers in spawn and in fruiting bodies inner tissue compared to the high concentration in mycelial-colonized straw. The majority of the 38 isolates belonged to phyla Firmicutes and Actinobacteria were identified as Bacillus, Paenibacillus and Micromonospora species. Similarly, 16S rRNA gene bacterial clones obtained from mycelial biomass DNA samples showed bacterial presence of various genera including Bacillus and Paenibacillus. In the mycelial growth promoting ability tests, 30 isolates negatively affected mycelial growth, two isolates showed no effect on mycelial growth, and six isolates promoted mycelial growth. Moreover, mycelial thickness was influenced in different ways by the bacterial growth. In general, nearly all isolates growth-preventing were isolated from healthy spawn and mycelial-colonized straw, whereas fruiting bodies were the best source for isolation of mycelial growth-promoting bacteria. Characterization of bacterial isolates revealed that growth-preventing isolates exhibited various enzymatic activities in comparison with positive influencing bacteria that exhibited none or weak enzymatic activities. In addition, the influence of volatile compounds being present in the headspace of bi-plate co-cultures on P. ostreatus mycelial growth was demonstrated. The effect of isolates, that promoted mycelial growth in co-cultivation, to reduce P. ostreatus spawn running time, was evaluated on sterilized rye seeds. Results showed that not all mycelial promoted isolates were able to significantly promote P. ostreatus colonization. However, isolate M46 F identified as Micromonospora lupini significantly reduce spawn running time. This is one of few studies to estimate cultivable bacteria from healthy samples of P. ostreatus cultivation, to evaluate a bacterial effect on mycelial growth, to show that fruiting bodies are a good source for mycelia growth-promoting isolates, and the first to report a shorter P. ostreatus spawn running time due to bacterial inoculation.

    更新日期:2019-12-13
  • The cell surface adhesins of Mycobacterium tuberculosis
    Microbiol. Res. (IF 3.701) Pub Date : 2019-12-09
    Vivek Vinod, Sukhithasri Vijayrajratnam, Anil Kumar Vasudevan, Raja Biswas

    Bacterial cell surface adhesins play a major role in facilitating host colonization and subsequent establishment of infection. The surface of Mycobacterium tuberculosis, owing to the complex architecture of its cell envelope, expresses numerous adhesins with varied chemical nature, including proteins, lipids, lipoproteins, glycoproteins and glycopolymers. Studies on mycobacterial adhesins show that they bind with multifarious host receptors and extracellular matrix (ECM) components. In this review we have highlighted the adhesins that are abundantly present on the mycobacterial surface and their interactions with host receptors. M. tuberculosis interacts with various host cell surface receptors such as toll like receptors, C-type lectin receptors, scavenger receptors, and Fc and complement receptors. Apart from these, ECM components like fibronectin, collagen, elastin, laminin, fibrillin and vitronectin also provide binding sites for surface adhesins of the tubercle bacilli. M. tuberculosis adhesins include proteins with and without signal peptide sequence and transmembrane proteins. Other surface adhesin macromolecules of M. tuberculosis comprises of lipids, glycolipids and glycopolymers. The interaction between the mycobacterial adhesins and their host receptors result in adhesion of the microbe to the host cells, induction of immune response and aid in the pathogenesis of the disease. A thorough understanding of the different M. tuberculosis surface adhesins and host receptors will provide a better picture of interaction between them at molecular level. The information gained on adhesins and host receptors will prove beneficial in developing novel therapeutic strategies such as the use of anti-adhesin molecules to hinder the adhesion of bacteria to the host cells, thereby preventing establishment of infection. The surface molecules discussed in this review will also benefit in identification of new drug targets, diagnostic markers or vaccine candidates against the deadly pathogen.

    更新日期:2019-12-09
  • Characterization the role of GacA-dependent small RNAs and RsmA family proteins on 2,4-diacetylphloroglucinol production in Pseudomonas fluorescens 2P24
    Microbiol. Res. (IF 3.701) Pub Date : 2019-12-09
    Yang Zhang, Bo Zhang, Xiaogang Wu, Li-Qun Zhang

    Pseudomonas fluorescens 2P24 is a plant-beneficial rhizobacteria that controls many root diseases caused by soil-borne pathogens, and the production of the antibiotic compound 2,4-diacetylphloroglucinol (2,4-DAPG) is essential for its biocontrol ability. In the present study, we investigated the regulatory mechanism acting on the production of 2,4-DAPG by the GacA-dependent small non-coding RNAs (sRNAs) and RsmA/E proteins in strain 2P24. Our results showed that the GacS-GacA system regulates the expression of the phlACBD locus, which is responsible for 2,4-DAPG production, by inducing the expression of rsmX, rsmX1, rsmY, and rsmZ. A novel GacA-regulated sRNA, RgsA, was found to negatively regulate 2,4-DAPG production. Activation of the phlACBD locus by the GacS-GacA system is mediated through RsmA and RsmE proteins (but not RsmI), which inhibit phlACBD translation by binding to the putative RsmA/E recognition element in the phlACBD leader. Taken together, our results suggested that in P. fluorescens 2P24, the GacS-GacA system controls the cellular 2,4-DAPG levels in the cell by fine-tuning the function of sRNAs in P. fluorescens.

    更新日期:2019-12-09
  • Community structures of the rhizomicrobiomes of cultivated and wild soybeans in their continuous cropping
    Microbiol. Res. (IF 3.701) Pub Date : 2019-12-06
    Lei Tian, Shaohua Shi, Lina Ma, Lam-Son Phan Tran, Chunjie Tian

    Continuous cropping of soybean often causes significant declines in yields of soybean because of the outbreaks of soil-borne fungal diseases. It has been reported that wild crops often harbour a unique microbiome to benefit the host plants. Thus, it is necessary to find the different community structures of the rhizomicrobiomes associated with cultivated and wild soybeans in their continuous cropping. In this study, we simulated monocropping of cultivated and wild soybeans under greenhouse conditions to investigate the rhizomicrobiomes of both soybeans. Results indicated that the bacterial community structure still maintained a changing trend after four continuous planting seasons, while fungal community structure showed a stable trend as indicated by the high similarity in the fungal community structure between the third and fourth planting rotations in both soybeans. In addition, by comparing the continuous cropping of the two soybeans, we found different fungal groups in their rhizospheres between the wild and cultivated soybeans following each passage. Spizellomycetaceae was more highly enriched in the rhizosphere following cultivation of the cultivated soybean, while Chaetomiaceae and Orbiliaceae were more highly enriched in the rhizosphere of wild soybean. Taken together, results of this study suggested that although there was the same trend of stabilized fungal development in the rhizospheres of both soybeans, wild soybean rhizosphere had different fungal groups compared with that of cultivated soybean following their continuous cropping. The findings of this study may provide useful information for the farmers with regard to planting soybean, especially when they consider growing soybean in monoculture.

    更新日期:2019-12-07
  • Rhizobacteria-induced systemic tolerance against drought stress in Sorghum bicolor (L.) Moench
    Microbiol. Res. (IF 3.701) Pub Date : 2019-11-30
    René Carlson, Fidele Tugizimana, Paul A. Steenkamp, Ian A. Dubery, Ahmed Idris Hassen, Nico Labuschagne
    更新日期:2019-11-30
  • Functional Characterization of Potential PGPR Exhibiting Broad-spectrum Antifungal activity
    Microbiol. Res. (IF 3.701) Pub Date : 2019-11-30
    Saira Ali, Sohail Hameed, Muhammad Shahid, Mazhar Iqbal, George Lazarovits, Asma Imran

    This study describes the biocontrol potential ofrhizobacteria against a range of fungal phytopathogens. Out of 227 bacteria isolated from the rhizosphere of maize, rice, wheat, potato, sunflower and soybean crops cultivated in different agro-ecological regions of Pakistan, 48 exhibited >60% antifungal activity againstFusarium oxysporum, Fusarium moniliforme, Rhizoctonia solani, Colletotrichum gloeosporioides, Colletotrichum falcatum, Aspergillus niger, and Aspergillus flavus. The rhizobacteria inhibiting > 65% pathogen growth were selected for detailed molecular and in planta studies most of which were identified as Pseudomonas and Bacillus species based on 16S rRNA gene sequence analysis. Antifungal metabolites produced by these rhizobacteria analyzed through LCMS were identified as antibiotics (iturin, surfactins, fengycin, DAPG, Phenazine, etc.), cell wall degrading enzymes(protease, chitinase, and cellulase), plant growth promotion enzymes and hormones (indole-3-acetic acid, ACC-deaminase, phosphates, nitrogen fixation), N-acyl-homoserine lactones and siderophores. Thegrowth room experimentvalidated the potential of these bacteria asbiofertilizer and biopesticide agents. Of all, P. aeruginosa strain FB2 andB. subtilis strain RMB5showed significantly higher potential as antagonistic plant-beneficial bacteria effective against a range of fungal phytopathogens. Both these bacteria can be used to develop a dual-purpose bacterial inoculum as biopesticide and biofertilizer. Rest of the antagonistic PGPR may be exploited for disease control in less-infested soils.

    更新日期:2019-11-30
  • 更新日期:2019-11-29
  • Ecological impact of a rare sugar on grapevine phyllosphere microbial communities
    Microbiol. Res. (IF 3.701) Pub Date : 2019-11-26
    Michele Perazzolli, Andrea Nesler, Oscar Giovannini, Livio Antonielli, Gerardo Puopolo, Ilaria Pertot

    Plants host a complex microbiota inside or outside their tissues, and phyllosphere microorganisms can be influenced by environmental, nutritional and agronomic factors. Rare sugars are defined as monosaccharides with limited availability in nature and they are metabolised by only few certain microbial taxa. Among rare sugars, tagatose (TAG) is a low-calories sweetener that stimulates and inhibits beneficial and pathogenic bacteria in the human gut microbiota, respectively. Based on this differential effect on human-associated microorganisms, we investigated the effect of TAG treatments on the grapevine phyllosphere microorganisms to evaluate whether it can engineer the microbiota and modify the ratio between beneficial and pathogenic plant-associated microorganisms. TAG treatments changed the structure of the leaf microbiota and they successfully reduced leaf infections of downy mildew (caused by Plasmopara viticola) and powdery mildew (caused by Erysiphe necator) under field conditions. TAG increased the relative abundance of indigenous beneficial microorganisms, such as some potential biocontrol agents, which could partially contribute to disease control. The taxonomic composition of fungal and bacterial leaf populations differed according to grapevine locations, therefore TAG effects on the microbial structure were influenced by the composition of the originally residing microbiota. TAG is a promising biopesticide that could shift the balance of pathogenic and beneficial plant-associated microorganisms, suggesting selective nutritional/anti-nutritional properties for some specific taxa. More specifically, TAG displayed possible plant prebiotic effects on the phyllosphere microbiota and this mechanism of action could represent a novel strategy that can be further developed for sustainable plant protection.

    更新日期:2019-11-27
  • Identification of mimp-associated effector genes in Fusarium oxysporum f. sp. cubense race 1 and race 4 and virulence confirmation of a candidate effector gene
    Microbiol. Res. (IF 3.701) Pub Date : 2019-11-18
    Wenjun Chang, Heng Li, Hanqing Chen, Fan Qiao, Huicai Zeng

    Effectors secreted by microbes contribute to pathogen virulence and/or avirulence on host plants in the interaction of plants and microbes. Also, the effector repertoire determines the host specificity of a pathogen. Fusarium oxysporum f. sp. cubense (Foc) is the causal agent of banana wilt; however, knowledge about Foc effector genes is very limited. In this study, genome-wide effector gene identification was performed in Foc race 1 (Foc 1) and Foc race 4 (Foc 4) based on the context association between the effector genes and the transposable element mimp. A total of 20 candidate effector genes were identified, of which 3 were Foc 1-specific, 6 were Foc 4-specific, and 11 were present in both Foc 1 and Foc 4. Most genes (14 out of 20) showed a significant transcriptional burst in planta compared with in-culture conditions, from more than 10-fold to 1,617-fold, and at the highest 32,725-fold. In addition to Foc 1- and Foc 4-specific genes, the genes Foc 283, Foc 495, and Foc 594 also exhibited transcriptional race specificity. Sixteen of the twenty genes were predicted to have a signal peptide, nine genes might encode real effectors predicted by EffectorP 2.0, and eight genes had predicted motifs. To validate the pathogenicity of the candidate effector genes, we generated knockout mutant and complementants of the gene Foc 1324 and tested their virulence on banana plants. The results showed that Foc 1324 was a virulent factor and required for the pathogenicity of Foc 4.

    更新日期:2019-11-18
  • Molecular and Biotechnological Aspects of Secondary Metabolites in Actinobacteria
    Microbiol. Res. (IF 3.701) Pub Date : 2019-11-12
    Richa Salwan, Vivek Sharma

    The ability to produce plethora of secondary metabolites and enzymes for pharmaceutical, agricultural and biotechnological applications make actinobacteria one of the most explored microbes among prokaryotes. The secondary metabolites and lytic enzymes of actinobacteria are known for their role in various physiological, cellular and biological processes including environmental sensing, mineral acquisition and recycling, and establishing social communication. In addition, the basic scaffold of secondary metabolties derived from actinobacteria is a source of inspiration for chemists. Recent development in “gene to metabolites” and “metabolites to gene” based omics technologies have played major role in revealing the prevalence of silent gene clusters in the genome of actinobacteria. Moreover, the development in precision-based genome editing tools and use of artificial gene operon for pathway engineering have emerged as a key player in activation of these silent/cryptic gene clusters for novel metabolites at large scale which were previously found to be poorly expressed and difficult to characterize in lab conditions. The access to diverse uncharacterized biosynthetic gene clusters of different types and the leverage of modern gene editing tools for modulated expression of the operons would contribute to novel product discovery and product diversification compared to traditional way of mining metabolites. Here, in review article, we have discussed the taxonomic status, genomic potential of actinobacteria for various secondary metabolites and role of genetic engineering to explore these microbes for human welfare.

    更新日期:2019-11-13
  • Biochar amendment controlled bacterial wilt through changing soil chemical properties and microbial community
    Microbiol. Res. (IF 3.701) Pub Date : 2019-11-11
    Shu Chen, Gaofu Qi, Gaoqiang Ma, Xiuyun Zhao

    Long-term continuous cropping has led to epidemic of bacterial wilt disease in Southern China. Bacterial wilt disease is caused by Ralstonia solanacearum and difficult to control. In order to control bacterial wilt, rice hull biochar was applied to soil with different doses (0, 7.5, 15, 30 and 45 t ha-1) in a field trial. After three years, the influence of biochar on soil properties, incidence of bacterial wilt and microbial community were characterized. Biochar amendment significantly suppressed bacterial wilt through changing soil chemical properties and microbial composition. Compared with control, disease incidence and index of biochar amendments (7.5, 15, 30, and 45 t ha-1) significantly decreased. Disease incidence and index of biochar amendment (15 t ha-1) were the lowest. Compared to the unamended control, contents of soil organic matter in biochar amendments (15, 30 t ha-1), available nitrogen in biochar amendment (15 t ha-1), and urease activity in biochar amendments (7.5, 15 t ha-1) significantly increased. Biochar amendments (15, 30, and 45 t ha-1) increased the relative abundances of potential beneficial bacteria (Aeromicrobium, Bacillus, Bradyrhizobium, Burkholderia, Chlorochromatium, Chthoniobacter, Corynebacterium, Geobacillus, Leptospirillum, Marisediminicola, Microvirga, Pseudoxanthomonas, Telmatobacter). Biochar amendments (7.5, 30, and 45 t ha-1) reduced the relative abundances of denitrifying bacteria (Noviherbaspirillum, Reyranella, Thermus). Biochar amendments (7.5, 15, and 45 t ha-1) significantly decreased pathogen Ralstonia abundance. Overall, application of biochar effectively controlled bacterial wilt through sequestering more carbon and nitrogen, enriching specific beneficial bacteria and decreasing pathogen abundance. This study revealed the potential of biochar in control of bacterial wilt.

    更新日期:2019-11-13
  • Mating-type switching and mating-type gene array expression in the methylotrophic yeast Ogataea thermomethanolica TBRC656
    Microbiol. Res. (IF 3.701) Pub Date : 2019-11-09
    Sriwan Wongwisansri, Peerada Promdonkoy, Somsak Likhitrattanapisal, Piyanun Harnpichanchai, Kazuhito Fujiyama, Yoshinobu Kaneko, Lily Eurwilaichitr, Supawadee Ingsrisawang, Sutipa Tanapongpipat

    The methylotrophic yeast, Ogataea thermomethanolica TBRC656, is an attractive host organism for heterologous protein production owing to the availability of protein expression vectors and a genome-editing tool. In this study, we focused on mating-type switching and gene expression in order to elucidate its sexual life cycle and establish genetic approaches applicable for the strain. A putative mating-type gene cluster was identified in TBRC656 that is syntenic to the cluster in Ogataea parapolymorpha DL-1 (previously named Hansenula polymorpha). Like DL-1, TBRC656 possesses two mating loci, namely MATa and MATα, and also shows flip-flop mating-type switching. Interestingly, unlike any other methylotrophic yeast, TBRC656 robustly switched mating type during late growth in rich medium (YPD). Under nutrient depletion, mating-type switching was observed within one hour. Transcription from both MATa and MATα mating loci was detected during growth in YPD, and possibly induced upon nitrogen depletion. Gene expression from MATα was detected as a single co-transcript from a three-gene array (α2-α1-a1S). Deletion of a putative a1S ORF at the MATα locus had no observed effect on mating-type switching but demonstrated significant effect on mating-type gene expression at both MATa and MATα loci.

    更新日期:2019-11-11
  • Colonization of the Gut Microbiota of Honey Bee (Apis mellifera) Workers at Different Developmental Stages
    Microbiol. Res. (IF 3.701) Pub Date : 2019-11-07
    Zhi-Xiang Dong, Huan-Yuan Li, Yi-Fei Chen, Feng Wang, Xian-Yu Deng, Lian-Bing Lin, Qi-Lin Zhang, Ji-Lian Li, Jun Guo

    The role of the gut microbiome in animal health has become increasingly evident. Although the structure of the gut microbiome of A. mellifera is well known, little is known about the dynamic change across different developmental stages. In this study, we explored the dynamic changes of the gut microbiota of A. mellifera at different developmental stages covering the whole life cycle using high-throughput 16S rRNA gene sequencing. The results indicated that the core (shared) gut microbiota changes significantly among different developmental stages. The diversity of the bacterial community in workers among different ages was significantly different. In addition, by comparing the core gut microbiota among different-aged workers, we found that newly emerged workers had fewer core microbiota. Three genera, Gilliamella, Frischella, and Snodgrassella, were significantly colonized at 1 day poste mergence (dpe); Lactobacillus, Bifidobacterium, Commensalibacter were significantly colonized at 3 dpe and significantly reduced with Gilliamella. Lactobacillus kunkeei and Bartonella were significantly colonized at 12 dpe and were significantly decreased with Lactobacillus helsingborgensis. Commensalibacter and Bifidobacterium were significantly decreased at 25 dpe, and Bacteroides, Escherichia-Shigella, and Porphyromonadaceae were significantly decreased between 19 and 25 dpe. Our results reveal the succession of the gut microbiota of workers from birth to senescence, which provides a theoretical basis for further exploring the roles of gut microbiota during different developmental stages.

    更新日期:2019-11-07
  • Isolation of Trichoderma from forestry model base and the antifungal properties of isolate TpsT17 toward Fusarium oxysporum
    Microbiol. Res. (IF 3.701) Pub Date : 2019-11-05
    Chang Zhou, Ruiting Guo, Shida Ji, Haijuan Fan, Jinjie Wang, Yucheng Wang, Zhihua Liu

    Eleven soil samples were collected from different plantations at the Forestry Model Base, Northeast Forestry University, China (45°43ʹ10″ N, 126°37ʹ15″ E), and 122 Trichoderma strains (T1–T122) were isolated. Nine Trichoderma species were identified based on morphological and molecular classification methods. The diversity of woody fungi was analyzed based on the type and quantity of Trichoderma spp. in the soil samples isolated from each plantation. Subdominant T. pseudoharzianum T17 (TpsT17) was screened and its biocontrol potential against Fusarium oxysporum CFCC86068 (Fox68) and growth promotion of Populus davidiana × P. alba var. pyramidalis (PdPap) seedlings were investigated. Compared with PdPap + Fox68 treatment, PdPap + TpsT17+Fox68 treatment had an obvious antagonistic effect on Fox68 based on the status of roots and stomata of the poplar seedlings. In addition, pretreatment with TpsT17 increased catalase activity 14-fold and decreased hydrogen peroxide and malondialdehyde concentrations 2.57- and 7-fold, respectively, in the PdPap + TpsT17+Fox68 treatment compared with the PdPap + Fox68 treatment. The transcription levels of PR1, JAZ6751, MYC2, MP, and JAR1 in PdPap + TpsT17+Fox68-treated plants were upregulated 5.75-, 5.63-, 14.88-, 8.24-, and 10.45-fold, respectively, at 3 d, while LAX2 exhibited little change in comparison with the level in PdPap + Fox-treated plants. TpsT17 was detected in the roots and stems of PdPap + TpsT17- and PdPap + TpsT17+Fox68-treated PdPap 28 d after inoculation, which demonstrated the endogenous capacity of TpsT17.

    更新日期:2019-11-06
  • The potential of endophytic fungi isolated from cucurbit plants for biocontrol of soilborne fungal diseases of cucumber
    Microbiol. Res. (IF 3.701) Pub Date : 2019-11-04
    Lin-Qi Huang, Yong-Chun Niu, Lei Su, Hui Deng, Heng Lyu

    The ability of endophytic fungi isolated from cucurbit plants to suppress soilborne diseases and the relationship between antagonism and disease suppression were studied. In dual culture tests of 1044 strains of 90 genera and three pathogenic fungi, 47.1% of the endophytic fungal strains showed antagonistic effects on at least one pathogen; 186 strains against Rhizoctonia solani, 371 strains against Sclerotinia sclerotiorum, and 403 strains against Fusarium oxysporum f. sp. cucumerinum. The main antagonistic type of the strains of one genus generally was identical to one pathogen. In the pot experiment of cucumber inoculated with R. solani and endophytic fungi, 74.3% and 33.3% of 288 strains showed control efficacy of more than 50% and more than 80% on cucumber Rhizoctonia root rot respectively. These strains were mostly distributed in Fusarium, Chaetomium, Colletotrichum and Acrocalymma. There were some differences in the proportion of strains with better disease suppressive effects between strain sources. No significant correlation existed between the disease suppression of a strain in vivo and its antagonism against the pathogen in vitro. Most growth-promoting strains had good suppressive effects on cucumber Rhizoctonia root rot. In this study, 82 endophytic fungal strains had good disease suppressive effects and no obvious adverse effects on cucumber growth, and 35 of them showed obvious growth-promoting effects, which suggested that endophytic fungi from cucurbit plants have excellent potential for plant disease control.

    更新日期:2019-11-04
  • The aldehyde dehydrogenase, AldA, is essential for L-1,2-propanediol utilization in laboratory-evolved Escherichia coli.
    Microbiol. Res. (IF 3.701) Pub Date : 2016-12-13
    Ramy K Aziz,Jonathan M Monk,Kathleen A Andrews,Jenny Nhan,Valerie L Khaw,Hesper Wong,Bernhard O Palsson,Pep Charusanti

    Most Escherichia coli strains are naturally unable to grow on 1,2-propanediol (PDO) as a sole carbon source. Recently, however, a K-12 descendent E. coli strain was evolved to grow on 1,2-PDO, and it was hypothesized that this evolved ability was dependent on the aldehyde dehydrogenase, AldA, which is highly conserved among members of the family Enterobacteriacea. To test this hypothesis, we first performed computational model simulation, which confirmed the essentiality of the aldA gene for 1,2-PDO utilization by the evolved PDO-degrading E. coli. Next, we deleted the aldA gene from the evolved strain, and this deletion was sufficient to abolish the evolved phenotype. On re-introducing the gene on a plasmid, the evolved phenotype was restored. These findings provide experimental evidence for the computationally predicted role of AldA in 1,2-PDO utilization, and represent a good example of E. coli robustness, demonstrated by the bacterial deployment of a generalist enzyme (here AldA) in multiple pathways to survive carbon starvation and to grow on a non-native substrate when no native carbon source is available.

    更新日期:2019-11-01
  • Erratum to “Proteomic analysis of differential protein expression in Acidithiobacillus ferrooxidans cultivated in high potassium concentration” [Microbiol. Res. 168 (7) (2013) 455–460].
    Microbiol. Res. (IF 3.701) Pub Date : 2016-04-12
    Jianping Ouyang,Wenbin Guo,Bo Li,Li Gu,Huijun Zhang,Huijun Xinhua Chen

    Acidithiobacillus ferrooxidans is a chemolithoautotrophic acidophile that oxidizes ferrous iron or sulfur compounds to obtain energy in the presence of various ions. To investigate the potassium ion response of A. ferrooxidans, we conducted a proteomics analysis. We identified eight proteins that were differentially expressed in the presence of high potassium concentration, including four up-regulated and four down-regulated proteins. Transcription levels of the genes encoding differential expressed proteins were subsequently analyzed by Northern blot in the presence of high potassium concentration. Among the up-regulated proteins, GDP-mannose 4,6-dehydratase, ribose 5-phosphate isomerase A and ribose-phosphate pyrophosphokinase were known to be implicated in the synthesis of glycocalyx, suggesting that the formation of glycocalyx might be involved in the A. ferrooxidans response to high potassium concentration. Thickening of the glycocalyx layer was also observed in cells cultivated under high potassium concentration via transmission electronic microscopy (TEM) analysis. Among the down-regulated proteins, ATP synthase F1 delta subunit and ATP synthase F1 beta subunit were two important components of ATP synthase. ATP synthase (P-ATPase) is directly linked to the transport of potassium into the cell, thus Acidithiobacillus ferrooxidans might just reduce the quantity of ATP synthase to offset the high potassium level in the culture medium. Therefore, the results obtained here provide some new clues to improve our understanding of the response of A. ferrooxidans to high potassium concentration.

    更新日期:2019-11-01
  • Characterization and partial purification of entomocin 110, a newly identified bacteriocin from Bacillus thuringiensis subsp. Entomocidus HD110.
    Microbiol. Res. (IF 3.701) Pub Date : 2009-02-14
    Ameur Cherif,Wafa Rezgui,Noura Raddadi,Daniele Daffonchio,Abdellatif Boudabous

    A new bacteriocin produced by Bacillus thuringiensis subsp. entomocidus was identified. The antibacterial activity termed entomocin 110 was produced starting at mid-logarithmic growth phase, reaching its maximum at the early and during stationary phase. The bacteriocin obtained from culture supernatant was inhibitory to several Gram-positive bacteria including Listeria monocytogenes, Paenibacillus larvae and other Bacillus species. Entomocin 110 was shown to be heat stable and resistant to pH variation and to organic solvents. The inhibitory activity was totally lost after proteinase K treatment, thereby revealing its proteinaceous nature. The mode of action of entomocin 110 was bactericidal and bacteriolytic. Upon partial purification with ammonium sulphate precipitation followed by butanol extraction, an active peptide with an apparent molecular weight of 4.8 kDa was identified. Cross inhibition tests with bacteriocin producer strains and plasmid profiles indicated that entomocin 110 is a new bacteriocin, which genetic determinants are probably harbored by the chromosome.

    更新日期:2019-11-01
  • Quantification of Bifidobacterium spp. and Lactobacillus spp. in rat fecal samples by real-time PCR.
    Microbiol. Res. (IF 3.701) Pub Date : 2009-02-14
    Jean-Marc Delroisse,Anne-Lise Boulvin,Isabelle Parmentier,Robin Dubois Dauphin,Micheline Vandenbol,Daniel Portetelle

    The microbiota of the rat intestinal tract constitutes a complex ecosystem of microorganisms. We have developed a real-time quantitative PCR assay based on genus-specific 16S rDNA primers and 3' minor groove binder (MGB) probes for accurate detection and quantification of a wide range of Bifidobacterium spp. (30 species) and Lactobocillus spp. (15 species) in rat fecal samples. Real-time PCR detection of serially diluted DNA isolated from reference strains of Bifidobacterium longum and Lactobacillus acidophilus was linear for cell counts ranging from 10(6) to 10 cells per PCR assay. The method proved applicable to the detection of Bifidobacterium spp. and Lactobacillus spp. at concentrations down to 10 CFU per PCR, corresponding to 5 x 10(4) CFU/g feces. The inter-extract reproducibility was high, with a coefficient of variation ranging from 0.24% to 1.07% for the Bifidobacterium assay and from 0.05% to 1.28% for the Lactobacillus assay. We conclude that real-time PCR is a very sensitive and precise technique for extensive quantitative evaluation of gut Bifidobacterium spp. and Lactobacillus spp. Thus, the approach used here to detect and quantify bacteria with group-specific primers should contribute to further studies of the composition and dynamics of the rat intestinal microbiota.

    更新日期:2019-11-01
  • Isolation, phylogenetic analysis and screening of marine mollusc-associated bacteria for antimicrobial, hemolytic and surface activities.
    Microbiol. Res. (IF 3.701) Pub Date : 2009-02-14
    Lyudmila A Romanenko,Masataka Uchino,Natalia I Kalinovskaya,Valery V Mikhailov

    This study was undertaken to survey culturable heterotrophic bacteria associated with the marine ark shell Anadara broughtoni inhabiting in the Sea of Japan, and to test isolates for their antimicrobial, hemolytic and surface activities with an emphasis on low-molecular-weight metabolites search. A total of 149 strains were isolated and identified phenotypically. A total of 27 strains were selected to be investigated phylogenetically by 165 rRNA gene sequence analysis. The most bacteria were affiliated with members of the Gammaproteobacteria and Alphaproteobacteria, and Less with Firmicutes, Actinobacteria, and Cytophaga-Flavobacterium-Bacteroides (CFB) group. The isolates capable of hemolysis were numerically abundant in the genera Pseudoalteromonas, Aeromonas and Bacillus. The six Gram-positive isolates belonging to the genera Bacillus, Paenibacillus and Saccharothrix and two Gram-negative strains related to Pseudomonas and Sphingomonas, possessed antimicrobial activity against indicator strains and to each other. Antimicrobial, hemolytic and surface activities were revealed in butanot extracts of cells or cell-free supernatant of six active strains. This points to availability of active low-molecular-weight metabolites. Substances with hemolytic and surface activities were isolated from strain Bacillus pumilus An 112 and characterized as cyclic depsipeptides with molecular masses 1021, 1035, 1049, 1063 and 1077 Da. The recovery of strains producing antimicrobial and surface-active substances suggests that microorganisms associated with the marine bivalve are potential source of bioactive metabolites.

    更新日期:2019-11-01
  • Production of FK520 by Streptomyces tubercidicus.
    Microbiol. Res. (IF 3.701) Pub Date : 2009-02-14
    Attila Kónya,Zsuzsanna Szabó,Ildikó Láng,István Barta,János Salát

    The discovery of immunosuppressant compounds created the conditions for the successful transplantations. Effective immunosuppressant compounds were isolated from cultures of different microorganisms, among others macrolide type immunosuppressants, FK506 and FK520, were isolated from the fermentation broths of Streptomyces species. In this study a screening program was carried out to isolate microorganisms, which produce macrolide type immunosuppressant compounds. More than 40,000 actinomycete strains were investigated in the screening program comprising chemical, microbiological and PCR methods for the investigation of the cultures. Actinomycete strains with FK520 biosynthesizing ability were isolated in the program, which were identified as isolates of the Streptomyces tubercidicus species according to the taxonomical investigations. A part of the 31-O-demethyl-FK520 methyltransferase gene of the isolated S. tubercidicus was sequenced and it showed 88% homology to that of Streptomyces hygroscopicus. Till now strains of the Streptomyces hygroscopicus species were known to produce FK520 and this study proved that strains of other Streptomyces species have FK520 biosynthetic ability.

    更新日期:2019-11-01
  • Anaerobic reduction of hexavalent chromium by bacterial cells of Achromobacter sp. Strain Ch1.
    Microbiol. Res. (IF 3.701) Pub Date : 2009-02-14
    Wenjie Zhu,Liyuan Chai,Zemin Ma,Yunyan Wang,Haijuan Xiao,Kun Zhao

    Hexavalent chromium [Cr(VI)] is a widespread environmental contaminant. Achromobacter sp. strain Chi was a Cr(VI) reducing bacterium with high reduction performance. Cr(VI) reductase was just existing in the cells, but was not discharged into the surrounding medium. Cr(VI) reduction was carried out with resting cells of strain Ch1 under anaerobic conditions. Initial pH value and lactate (electron donor) concentration were found to influence the reduction rate of Cr(VI), and the optimal conditions were at pH 9.0 and supplemented with 40 mM of lactate. The reduction rate would be constant under established conditions approximately 12.5 micromol 10(9) cells(-1) min(-1), which was not affected by cell density and initial Cr(VI) concentration. The maximal reduction capacity of Achromobacter sp. strain Ch1 was 54.2 mM, while the cell density of reduction system was 3.64 x 10(9) cells ml(-1). Energy-dispersive X-ray (EDX) analysis showed that chromium was precipitated perhaps as the form of Cr(OH)3.

    更新日期:2019-11-01
  • Construction of highly attenuated Salmonella enterica serovar Typhimurium live vectors for delivering heterologous antigens by chromosomal integration.
    Microbiol. Res. (IF 3.701) Pub Date : 2009-02-14
    Mohamed I Husseiny,Michael Hensel

    Attenuated live Salmonella enterica serovar Typhimurium is a versatile organism for the generation of live recombinant vaccines for mucosal immunization and various approaches were devised for the stable and efficient expressions of heterologous antigens by attenuated S. enterica strains. Phage lamda Red recombinase has recently been devised for gene replacements in S. enterica after introduction of PCR products as a one-step deletion approach and FLP-mediated recombination allows the subsequent removal of antibiotic resistance markers. As an extension of this method, we have developed an approach that allows the sequential integration of multiple recombinant expression cassettes for heterologous antigens into the chromosome of S. enterica. We observed the stable expression of model antigens without selective pressure. In addition, the method allows the simultaneous generation of double-attenuating mutations by gene deletions. This approach allows the rapid and efficient construction of recombinant Salmonella strains as vaccine carriers.

    更新日期:2019-11-01
  • Growth and siderophore production of Xylella fastidiosa under iron-limited conditions.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-11-01
    Maria Estela Silva-Stenico,Flávia Tereza Hansen Pacheco,Jorge Luiz Mazza Rodrigues,Emanuel Carrilho,Siu Mui Tsai

    In this study, the production of siderophores by Xylella fastidiosa from the citrus bacteria isolate 31b9a5c (FAPESP - ONSA, Brazil) was investigated. The preliminary evidence supporting the existence of siderophore in X. fastidiosa was found during the evaluation of sequencing data generated in our lab using the BLAST-X tool, which indicated putative open reading frames (ORFs) associated with iron-binding proteins. In an iron-limited medium siderophores were detected in the supernatant of X. fastidiosa cultures. The endophytic bacterium Methylobacterium extorquens was also evaluated. Capillary electrophoresis was used to separate putative siderophores produced by X. fastidiosa. The bacterial culture supernatants of X. fastidiosa were identified negative for hydroxamate and catechol and positive for M. extorquens that secreted hydroxamate-type siderophores.

    更新日期:2019-11-01
  • Effect of environmental factors on production of lichenin, a chromosomally encoded bacteriocin-like compound produced by Bacillus licheniformis 26L-10/3RA.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-05-11
    Priyabrata Pattnaik,Sunita Grover,Virender Kumar Batish

    Effect of environmental factors on production of lichenin, a bacteriocin-like compound produced by Bacillus licheniformis 26L-10/3RA isolated from buffalo rumen was studied. Lichenin represents the first anaerobiosis-specific expression of broad-spectrum antibacterial compound effective only under anaerobic conditions. Production of lichenin by B. licheniformis 26L-10/3RA was found to be very high at 39 degrees C in L-10 medium supplemented with 0.5% glucose and 20% (w/v) inert thermocol beads. Lichenin production was highest at pH 6.8 after 72-96h of incubation. Our study also indicated that Lichenin is not a plasmid-linked characteristic and is encoded by chromosomal DNA. Results obtained can be used in large-scale production of Lichenin for potential application in manipulating rumen function intended for improving productivity of the ruminants.

    更新日期:2019-11-01
  • Pore formation, polymerization, hemolytic and leukotoxic effects of a new Enterobacter cloacae toxin neutralized by antiserum.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-05-11
    María Gabriela Paraje,Alberto Jorge Eraso,Inés Albesa

    A new toxin of Enterobacter cloacae was purified and studied by SDS-PAGE electrophoresis with the purpose of investigating its ability to generate polymers and their molecular mass. Monomer of 13.3 kDa and structures of multimeric mass were detected. The toxin of 66 kDa was the most abundant form of toxin. This polymer and the monomer were selected to examine blood cells damage. Membrane pores caused by both toxin forms seemed to be of similar dimension (estimated in 3.6 nm by experiments with osmotic protectors) and were able to lyse erythrocytes and leukocytes. The results obtained indicate that polymerization and pore formation are involved in the molecular events that participate in the cytotoxic effects of E. cloacae toxin. Immunization of rabbits with 13.3kDa toxin generated antibody response capable of inhibiting oxidative stress as well as hemolytic and leukotoxic effects. Immunoblotting indicated that monomer and polymer reacted with antihemolysin serum. The importance of E. cloacae toxin "in vivo" was studied in animals by means of assays performed in peritoneum of rats, inoculated with the hemolytic strain (C1) and a non-hemolytic variant (C4). Both strains stimulated infiltration of leukocytes in peritoneum, but C1 caused cell death and lysis wheras assays with C4 maintained the viability of leukocytes even within 5 h after extraction of samples.

    更新日期:2019-11-01
  • Chemical compositions and antimicrobial activities of four different Anatolian propolis samples.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-05-11
    Ataç Uzel,Kadriye Sorkun,Ozant Onçağ,Dilşah Cogŭlu,Omür Gençay,Bekir Salih

    Propolis means a gum that is gathered by bees from various plants. It is known for its biological properties, having antibacterial, antifungal and healing properties. The aims of this study were to evaluate the antimicrobial activity of four different Anatolian propolis samples on different groups of microorganisms including some oral pathogens and comparison between their chemical compositions. Ethanol extracts of propolis (EEP) were prepared from four different Anatolian propolis samples and examined whether EEP inhibit the growth of the test microorganisms or not. For the antimicrobial activity assays, minimum inhibitory concentrations (MIC) were determined by using macrodilution method. The MIC values of the most effective propolis (TB) were 2 microg/ml for Streptococcus sobrinus and Enterococcus faecalis, 4 microg/ml for Micrococcus luteus, Candida albicans and C. krusei, 8 microg/ml for Streptococcus mutans, Staphylococcus aureus, Staphylococcus epidermidis and Enterobacter aerogenes, 16 microg/ml for Escherichia coli and C. tropicalis and 32 microg/ml for Salmonella typhimurium and Pseudomonas aeruginosa. The chemical compositions of EEP's were determined by high-temperature high-resolution gas chromatography coupled to mass spectrometry. The main compounds of four Anatolian propolis samples were flavonoids such as pinocembrin, pinostropin, isalpinin, pinobanksin, quercetin, naringenin, galangine and chrysin. Although propolis samples were collected from different regions of Anatolia all showed significant antimicrobial activity against the Gram positive bacteria and yeasts. Propolis can prevent dental caries since it demonstrated significant antimicrobial activity against the microorganisms such as Streptococcus mutans, Streptococcus sobrinus and C. albicans, which involves in oral diseases.

    更新日期:2019-11-01
  • Improvement of trypanocidal metabolites production by Aspergillus fumigatus using neural networks.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-05-11
    Niege Araçari Jacometti Cardoso Furtado,Marta Cristina Teixeira Duarte,Sérgio de Albuquerque,Cesar Mello,Jairo Kenupp Bastos

    An optimization procedure using artificial neural networks was developed to determine the optimal combination of parameters, such as medium culture, initial pH, temperature and time of fermentation for maximal trypanocidal metabolites production by Aspergillus fumigatus. A data set of 81 experiments was carried out and an artificial neural network was trained to identify the optimal conditions for this process. Good correlation was obtained between the experimental and predicted values of lysis of the trypomastigote forms of Trypanosoma cruzi (r2 = 0.9990). The simulations of fermentation performance were undertaken on combinations of input variables and the highest level of activity against T. cruzi was obtained from the chloroform extract of the modified Jackson medium culture, initial pH of 6.0, incubated at 40 degrees C for 144 h. It displayed lysis of 95% of the trypomastigote forms of T. cruzi and the red blood cells remained normal.

    更新日期:2019-11-01
  • In vitro activity of three different antimicrobial agents against ESBL producing Escherichia coli and Klebsiella pneumoniae blood isolates.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-05-11
    Ahmet Kizirgil,Kutbettin Demirdag,Mehmet Ozden,Yasemin Bulut,Yusuf Yakupogullari,Zulal Asci Toraman

    Extended spectrum beta-lactamases (ESBLs) usually associated with multiple drug resistance, including beta-lactam and non-beta-lactam antibiotics. This resistance can cause Limitation in the choice of drugs appropriate for using in clinical practice, especially in life-threatening infections. In this study we aimed to investigate in vitro activity of meropenem, ciprofloxacine and amikacin against ESBL-producing and non-producing blood isolates of Escherichia coli and Klebsiella pneumoniae strains. Fifty-eight E. coli (21 ESBL-producing, 37 non-ESBL producing) and 99 K. pneumoniae (54 ESBL-producing, 45 non-ESBL producing) strains were included in the study. The presence of ESBL was investigated by double disk synergy test and E-test methods. Antibiotic susceptibility test was done by microdilution method according to NCCLS guideline. In vitro susceptibilities of ESBL producing E. coli and K. pneumoniae strains were found as 100% for meropenem, 33.3% and 25.9% for ciprofloxacine, 94.5% and 83.3% for amikacin. It was observed that; meropenem was equally active agent in both ESBL-producing and non-producing strains, and its activity was not affected by ESBL production. Whereas amikacin activity was minimally affected and ciprofloxacine activity was markedly decreased by ESBL production. In conclusion, meropenem seems to be better choice of antibiotic should be used for ESBL positive life-threatening infections, because of remaining highest activity.

    更新日期:2019-11-01
  • Microbial metabolism of 2-chlorophenol, phenol and rho-cresol by Rhodococcus erythropolis M1 in co-culture with Pseudomonas fluorescens P1.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-05-11
    M Goswami,N Shivaraman,R P Singh

    Chlorophenolic waste most often contains phenol and rho-cresol along with chlorophenols. A Rhodococcus erythropolis strain M1 was isolated with the ability to degrade 2-chlorophenol, phenol and p-cresol (100 mgl(-1), each) in 18, 24 and 20 h, respectively, with negligible lag. However, Rhodococcus sp. characterized by low growth rate, pose a threat to be outgrown by bacteria occurring in natural habitats. In the present study, interaction of R. erythropolis M1 with another isolated bacteria generally encountered in activated sludge for water treatment like Pseudomonas fluorescens P1 was studied. 2-chlorophenol, phenol and p-cresol were selected as the substrates for the study. Viable cell counts showed competitive interaction between the species on 2-chlorophenol and phenol. Specific growth rate of pure culture of R. erythropolis M1 was higher than P. fluorescens P1 on 2-chlorophenol. However, in mixed culture, P. fluorescens P1 showed higher growth rate. Degradation of phenol showed higher growth rate of R. erythropolis M1 both in pure and in mixed culture form. Degradation of p-cresol had shown similar counts for both populations indicating neutral type of interaction. This observation was substantiated by detecting the growth rate, where both cultures had similar growth rate in pure and in the mixed culture form. Rate of 2-chlorophenol degradation was higher when R. erythropolis M1 was used as the pure culture as compared to the degradation rates observed with the P. fluorescens P1 or with the mixed culture. However, in case of phenol and p-cresol, degradation by the mixed culture had resulted in higher degradation rates as compared to the degradation of the substrates by both the axenic cultures.

    更新日期:2019-11-01
  • Antibacterial property of the antipsychotic agent prochlorperazine, and its synergism with methdilazine.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-03-24
    Laxmi Rani Basu,Kaushiki Mazumdar,Noton Kumar Dutta,Prithviraj Karak,Sujata G Dastidar

    The antipsychotic drug prochlorperazine was screened in vitro for possible antimicrobial property against 157 strains of bacteria, belonging to gram positive and gram negative genera. The minimum inhibitory concentration (MIC) of prochlorperazine was determined by agar dilution method, which ranged from 25 to 200 microg/ml with respect to most of the strains. Based on such findings, a further study was undertaken to determine whether the efficacy of this drug could be enhanced in the presence of an antihistaminic agent methdilazine, reported to have remarkable antimicrobial action. Four bacterial strains, sensitive to prochlorperazine as well as to three antibacterial chemotherapeutics, viz., methdilazine, fluphenazine and thioridazine were chosen. Disc diffusion tests with prochlorperazine and methdilazine revealed marked synergism between the combination, compared to their individual effects. The synergism was found to be statistically significant (p<0.01). To assess the degree of synergism, the checkerboard analysis was performed. The FIC index of this combination turned out to be 0.37, which confirmed synergism. Therefore, this synergistic drug combination might open a new therapeutic approach to combat drug-resistance in bacterial infections.

    更新日期:2019-11-01
  • Diversity of ectomycorrhizal fungi naturally established on containerised Pinus seedlings in nursery conditions.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-03-24
    Khalid El Karkouri,Francis Martin,J P Emmanuel Douzery,Daniel Mousain

    The study examined the diversity of ectomycorrhizal fungi, naturally established on roots of containerised Pinus seedlings in a nursery, using PCR-RFLP and sequencing of the nuclear ribosomal internal transcribed spacer. Seventy-two samples, including ectomycorrhizae and fruit bodies, were examined. Molecular typing assigned the fungal symbionts to four ectomycorrhizal Boletales: Rhizopogon rubescens, Suillus bovinus, S. variegatus, and R. luteolus. R. rubescens was abundant (37.5%), while Suillus and R. luteolus species were moderately established (25-26%) and rare (2.8%), respectively. In addition, Rhizopogon species colonised P. nigra ssp. salzmannii seedlings, whereas Suillus species were identified on Pinus nigra ssp. nigra seedlings. The diversity and the ability of these naturally established symbionts under artificial nursery conditions were discussed. The molecular survey investigated here should contribute to successful monitoring of mycorrhizal application under both nursery and plantation conditions.

    更新日期:2019-11-01
  • Molecular typing of Klebsiella pneumoniae isolates from public hospitals in Recife, Brazil.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-03-24
    Ana Catarina de Souza Lopes,Juliana Falcão Rodrigues,Marcos Antônio de Morais Júnior

    Thirty nosocomial isolates of Klebsiella pneumoniae, collected from three public hospitals in Recife, Brazil, between 1999 and 2000, were analysed in order to determine their epidemiological relatedness and genetic characteristics. The isolates were characterised by biotyping, antibiotyping, protein analysis, plasmid profile and random amplified polymorphic DNA (RAPD). The majority of the clinical isolates were resistant to multiple antibiotics, in particular to beta-lactams, and 30% were found to be ESBLs producers. RAPD proved to be the most effective technique in discriminating unrelated K. pneumoniae isolates. It was confirmed by the highly genetic similarity found among related isolates from an hospital outbreak. We conclude that K. pneumoniae infections in Recife has been caused by a variety of bacterial genotypes. This is the first report that revealed the subtypes of K. pneumoniae in Brazil by plasmid analysis and RAPD.

    更新日期:2019-11-01
  • Antibacterial activity from Penicillium corylophilum Dierckx.
    Microbiol. Res. (IF 3.701) Pub Date : 2005-01-14
    Marley Garcia Silva,Niege Araçari Jacometti Cardoso Furtado,Mônica Tallarico Pupo,Maria José Vieira Fonseca,Suraia Said,Ademar Alves da Silva Filho,Jairo Kenupp Bastos

    A strain of Penicillium corylophilum isolated from Brazilian soil sample was submitted to different culture conditions to investigate the production of secondary metabolites with antimicrobial activity. The largest number of conidia was obtained after 5 days of incubation in oat medium and the highest level of antimicrobial activity was produced when the fungus culture was developed in the Czapek medium. The activity against Staphylococcus aureus was found only in the chloroform extract from Czapek culture broth, which also showed activity against Micrococcus luteus. Fumiquinozoline F was isolated from the active chloroform extract by using chromatographic methods. The minimal inhibitory concentration (MIC) values for M. luteus and S. aureus were 99 microg/ mL and 137microg/mL, respectively.

    更新日期:2019-11-01
  • Extracellular proteases from eight psychrotolerant Antarctic strains.
    Microbiol. Res. (IF 3.701) Pub Date : 2004-08-06
    Susana C Vazquez,Silvia H Coria,Walter P MacCormack

    Extracellular proteases from 8 Antarctic psychrotolerant Pseudomonas sp. strains were purified and characterised. All of them are neutral metalloproteases, have an apparent molecular mass of 45kDa, optimal activity at 40 degrees C and pH 7-9, retaining significant activity at pH 5-11. With the exception of P96-18, which is less stable, all retain more than 50% activity after 3 h of incubation at pH 5-9 and show low thermal stability (their half-life times range from 20 to 60 min at 40 degrees C and less than 5 min at 50 degrees C). These proteases can be used in commercial processes carried out at neutral pH and moderate temperatures, and are of special interest for their application in mixtures of enzymes where final thermal selective inactivation is needed. Results also highlight the relevance of Antarctic biotopes for the isolation of protease-producing enzymes active at low temperatures.

    更新日期:2019-11-01
  • Microbial diversity of soil from two hot springs in Uttaranchal Himalaya.
    Microbiol. Res. (IF 3.701) Pub Date : 2004-08-06
    Bhavesh Kumar,Pankaj Trivedi,Anil Kumar Mishra,Anita Pandey,Lok Man S Palni

    Soil samples collected from two hot springs, Soldhar and Ringigad, both located in the Garhwal region of Uttaranchal Himalaya were analysed for their physical, chemical and microbial components. The alkaline pH, total absence of carbon and nitrogen, and high temperature were features common to soil samples from both sites. The Soldhar samples contained higher amounts of Cu, Fe and Mn. Ringigad soil was devoid of Cu, but had much higher phosphate. While the optimum incubation temperature for isolating the maximum microbial counts from soil samples from the two sites was 50 degrees C, microbial growth in broth was also observed when incubated at 80 degrees C. Microscopic examination revealed three types of microbial populations, i.e., bacteria, yeast and filamentous organisms. The soil samples were found to be dominated by spore forming rods. Out of 58 aerobic isolates, 53 were gram positive bacilli. Gram positive anaerobic oval rods were also observed up to 60 degrees C. Soil dilution plates revealed the presence of antagonistic and phosphate solubilizing populations.

    更新日期:2019-11-01
  • During stationary phase, Beijerinckia derxii shows nitrogenase activity concomitant with the release and accumulation of nitrogenated substances.
    Microbiol. Res. (IF 3.701) Pub Date : 2004-01-14
    Natália Reiko Sato Miyasaka,Daniela Strauss Thuler,Eny Iochevet Segal Floh,Walter Handro,Mariana Braga Duarte Toledo,Sônia Maria Gagioti,Heloiza Ramos Barbosa

    Beijerinckia derxii, a free-living nitrogen-fixing bacterium, maintained an increasing nitrogenase specific activity during the stationary growth phase. To verify the destination of the nitrogen fixed during this phase, intra and extracellular nitrogenated contents were analyzed. Organic nitrogen and amino acids were detected in the supernatant of the cultures. An increase in intracellular content of both nitrogen and protein occurred. Cytoplasmic granules indicated the presence of arginine. The ability of a non-diazotrophic bacterium (E. coli) to use B. derxii proteins as a source of nitrogen was observed concomitantly with E. coli growth. There is a suggestion that B. derxii contributes to the environment by both releasing nitrogenated substances and accumulating substances capable of being consumed after its death.

    更新日期:2019-11-01
  • Prospore membrane formation: how budding yeast gets shaped in meiosis.
    Microbiol. Res. (IF 3.701) Pub Date : 2003-08-09
    Alexandra C Moreno-Borchart,Michael Knop

    During meiosis in Saccharomyces cerevisiae four daughter cells, called spores, are generated within the boundaries of the mother cell. This cell differentiation process requires de novo synthesis of prospore membranes (PSMs), which are the precursors of the spore plasma membranes. Assembly of these membranes is initiated at the spindle pole bodies (SPBs) during meiosis II. At this stage of the cell cycle, 4 SPBs are present. Two different meiosis-specific structures are known to be required for PSM formation. At the SPBs, specialized attachments, called the meiotic plaques, provide the required functionality necessary for the recruitment and assembly of the membranes. During subsequent membrane elongation, a second structure becomes important. This proteinaceous assembly forms a coat, called the leading edge protein coat (LEP coat), which covers the boundaries of the membranes. Assembly of the coat occurs at sites next to the SPBs, whereas its disassembly is concomitant to the closure of the membranes. This mini review discusses our current understanding of how the meiotic plaque and the LEP coat might function during biogenesis of the prospore membrane.

    更新日期:2019-11-01
  • The two enantiospecific dichlorprop/alpha-ketoglutarate-dioxygenases from Delftia acidovorans MC1--protein and sequence data of RdpA and SdpA.
    Microbiol. Res. (IF 3.701) Pub Date : 2002-12-28
    Anne Westendorf,Dirk Benndorf,Roland H Müller,Wolfgang Babel

    Two alpha-ketoglutarate-dependent dioxygenases carrying enantiospecific activity for the etherolytic cleavage of racemic phenoxypropionate herbicides [(RS)-2-(2,4-dichlorophenoxy)propionate and (RS)-2-(4-chloro-2-methylphenoxy)propionate] from Delftia acidovorans MC1 were characterized with respect to protein and sequence data. The (S)-phenoxypropionate/alpha-ketoglutarate-dioxygenase (SdpA) appeared as a monomeric enzyme with a molecular weight of 32 kDa in the presence of SDS. N-terminal sequences revealed relationship to alpha-ketoglutarate-dependent taurine dioxygenase (TauD) and to 2,4-dichlorophenoxyacetate/alpha-ketoglutarate-dioxygenase (TfdA). The (R)-phenoxypropionate/alpha-ketoglutarate-dioxygenase (RdpA) referred to 36 kDa in the presence of SDS and to 108 kDa under native conditions. Internal sequences of fragments obtained after digestion made evident relationship to TfdA and TauD. Two-dimensional electrophoretic separation resulted in the resolution of up to 3 individual spots with almost identical molecular weights but different isoelectric points with both RdpA and SdpA. The structural differences of these isoenzyme forms are not yet clear.

    更新日期:2019-11-01
  • Genomic fingerprinting of Bradyrhizobium japonicum isolates by RAPD and rep-PCR.
    Microbiol. Res. (IF 3.701) Pub Date : 2002-10-26
    Sanja Sikora,Sulejman Redzepović,Mihaela Bradić

    Genetic diversity of indigenous Bradyrhizobium japonicum population in Croatia was studied by using different PCR-based fingerprinting methods. Characteristic DNA profiles for 20 B. japonicum field isolates and two reference strains were obtained using random primers (RAPD) and two sets of repetitive primers (REP- and ERIC-PCR). In comparison with the REP, the ERIC primer set generates fingerprints of lower complexity, but still several strain-specific bands were detected. Different B. japonicum isolates could be more efficiently distinguished by using combined results from REP- and ERIC-PCR. The most polymorphic bands were observed after amplification with four different RAPD primers. Both methods, RAPD and rep-PCR, resulted in identical grouping of the strains. Cluster analysis, irrespective of the fingerprinting method used, revealed that all the isolates could be divided into three major groups. Within the major groups, the degree of relative similarity between B. japonicum isolates was dependent upon the method used. Our results indicate that both RAPD and rep-PCR fingerprinting can effectively distinguish different B. japonicum strains. RAPD fingerprinting proved to be slightly more discriminatory than rep-PCR.

    更新日期:2019-11-01
  • Survival of enterobacteria in liquid cultures during microwave radiation and conventional heating.
    Microbiol. Res. (IF 3.701) Pub Date : 1995-09-01
    C Papadopoulou,D Demetriou,A Panagiou,S Levidiotou,H Gessouli,K Ionnides,G Antoniades

    Bacteria in food have been reported to survive in larger numbers after processing by microwave radiation than after conventional processing. The bactericidal effect of a domestic microwave oven (SHARP R-7280) on certain pathogenic enterobacteria species was investigated in vitro, in comparison with conventional heating (boiling). The death rates of different nosocomial strains of Escherichia coli, Salmonella sofia, Salmonella enteritidis, Proteus mirabilis and Pseudomonas aeruginosa were tested. The microwave oven and the conventional heating system used were both calibrated in order to calculate temperatures from exposure times. For each strain duplicate samples of 25 ml of pure culture with concentrations at least 10(6) cfu/ml were exposed to microwave radiation. An equal number of samples of the same volume and concentration were exposed to conventional heating. Subsequently all samples were examined qualitatively and quantitatively following standard microbiological procedures. The results indicate that microwaves have an efficient bactericidal effect on the enterobacteria in liquid cultures.

    更新日期:2019-11-01
  • Factors affecting the adsorption of buchnericin LB, a bacteriocin produced by Lactobacillus [correction of Lactocobacillus] buchneri.
    Microbiol. Res. (IF 3.701) Pub Date : 2002-05-11
    Zeliha Yildirim,Yahya Kemal Avşar,Metin Yildirim

    Buchnericin-LB adsorbs to gram-positive but not to gram-negative bacteria. The tested gram-positive bacteria were species of Lactobacillus, Pediococcus, Leuconostoc, Enterococcus, Lactococcus, Listeria, Bacillus, Staphylococcus; gram-negative bacteria belonged to the genera Salmonella, Escherichia, Yersinia and Pseudomonas. Buchnericin-LB adsorption depended on pH but not on time and temperature. Also some anions of salts and lipoteichoic acid reduced or inhibited its adsorption. Treatment of cells and cell walls of sensitive bacteria with detergents, organic solvents or enzymes did not affect subsequent binding of buchnericin-LB. Treatment with buchnericin-LB caused sensitive cells to lose high amounts of intracellular K+ ions and UV-absorbing materials and became more permeable to o-nitrophenol-beta-D-galactopyranoside. Buchnericin-LB (640-2560 AU/ml) decreased the colony forming units (99%) and absorbance values of Listeria monocytogenes and Bacillus cereus. These results indicate that the mode of action of buchnericin-LB is bactericidal and its lethal effect is very rapid.

    更新日期:2019-11-01
  • Effect of lacZY-marking of the 2,4-diacetyl-phloroglucinol producing Pseudomonas fluorescens-strain 5-2/4 on its physiological performance and root colonization ability.
    Microbiol. Res. (IF 3.701) Pub Date : 2002-03-26
    Beatrix Waechter Alsanius,Malin Hultberg,Jan-Eric Englund

    Transgenic Pseudomonas fluorescens 5-2/4 with reinforced 2,4-diacetyl phloroglucinol (phl) production had shown increased biocontrol ability towards Pythium ultimum (Pu), but inferior root colonization ability compared to its wild type 5.014. Therefore, enhanced root colonization ability of the transgenic strain by repeated inoculation and reisolation on tomato plants was suggested. As a preparation for repeated inoculation and reisolation cycles, the construction of a negative control of the transgenic strain 5-2/4 by marking with lacZY and screening for a mutant possessing qualities comparable to 5-2/4 was performed. Morphologically, colonies of all of the 11 selected mutants were similar on MLXgal medium. The root colonization ability of two of the lacZY-marked strains (mutants 1 and 10) was comparable to the parental strain. These were also able to compete with the resident microflora of tomato seedlings to the same extent as the parental strain. Five mutants were excluded due to lower growth rates on Yeast Malt, King's B Medium (KB) and 0.1 Tryptic Soy Agar (mutant 4, 5 and 8), excessive growth and higher siderophore production on KB (mutant 10) and increased protease production (mutant 2). With respect to in vitro-antagonism of Pu, no differences could be found between the target strain and mutants 1, 3, 6, 7 and 9. Examination of sole carbon source utilization of these five lacZY-marked strains revealed a significantly higher utilization of alpha-D-lactose and lactulose compared to 5-2/4. However, significant differences could be found for 51% of the utilized carbon sources. Cluster analysis showed a high degree of similarity between 5-2/4 and mutant 1 both when analyzed with and without alpha-D-lactose. As mutant 1 also represented the colonization pattern most similar to the parental strain 5-2/4, it presents a presumptive subject for a negative control in the following inoculation and reisolation studies on tomato.

    更新日期:2019-11-01
  • Purification and partial characterization of exopolygalacturonase I from Penicillium frequentans.
    Microbiol. Res. (IF 3.701) Pub Date : 2002-03-26
    Maria Angélica dos Santos Cunha Chellegatti,Maria José Vieira Fonseca,Suraia Said

    A polygalacturonase with a molecular mass of 74 kDa, an isoelectric point around pH 4.2 and pH--and temperature optima of 3.9 and 50 degrees C, respectively, was purified from a culture fluid of Penicillium frequentans. The enzyme was characterized as an exo-alpha-1,4-polygalacturonase (exo-PG I). Km and Vmax for sodium polypectate hydrolysis were 0.68 g/l and 596.8 U x mg(-1), respectively. The enzyme, a glycoprotein with a carbohydrate content of 81%, is probably the main pectinase of Penicillium frequentans responsible for cleaving monomer units from the non-reducing end of pectin.

    更新日期:2019-11-01
  • Methane production in rice soil is inhibited by cyanobacteria.
    Microbiol. Res. (IF 3.701) Pub Date : 2002-03-26
    Radha Prasanna,Vinod Kumar,Sushil Kumar,Ashok Kumar Yadav,Upasana Tripathi,Atul Kumar Singh,M C Jain,Prabhat Gupta,P K Singh,N Sethunathan

    The present study was aimed at understanding the role of cyanobacteria and Azolla in methane production and oxidation in laboratory simulation experiments using soil samples from rice fields. All the seven cyanobacterial strains tested effected a significant decrease in the headspace concentration of methane in flooded soil, incubated under light. Synechocystis sp. was the most effective in retarding methane concentration by 10-20 fold over that in controls without cyanobacteria. The decrease in the headspace concentration of methane was negligible in nonsterile soil samples, inoculated with Synechocystis sp. and then incubated under dark. Moist soil cores (0-5 cm depth), collected from rice fields that had been treated with urea in combination with a cyanobacterial mixture, Azolla microphylla, or cyanobacterial mixture plus A. microphylla, effected distinctly more rapid decrease in the headspace concentration of methane added at 200 microl(-1) than did the soil cores from plots treated with urea alone (30, 60, 90 and 120 kg N ha(-1)), irrespective of the rate of chemical nitrogen applied to rice fields. Besides, soil cores from plots treated with urea alone at 60, 90 and 120 kg N ha(-1) oxidised methane more rapidly than did the core samples from plots treated with urea alone at 30kg N ha(-1). Cyanobacteria and A. microphylla, applied to flood water, appear to play a major role in mitigation of methane emission from rice fields-through enhanced methane oxidation.

    更新日期:2019-11-01
  • Perchlorate and nitrate reductase activity in the perchlorate-respiring bacterium perclace.
    Microbiol. Res. (IF 3.701) Pub Date : 2002-01-05
    T Giblin,W T Frankenberger

    The perchlorate (ClO4(-))-respiring organism, strain perclace, can grow using nitrate (NO3(-)) as a terminal electron acceptor. In resting cell suspensions, NO(-) grown cells reduced ClO4(-), and ClO4(-) grown cells reduced NO3(-). Activity assays showed that nitrate reductase (NR) activity was 1.31 micromol min(-1) (mg protein)-1 in (ClO4)- grown cells, and perchlorate reductase (PR) activity was 4.24 micromol min(-1) (mg protein)(-1) in NO3(-) grown cells. PR activity was detected within the periplasmic space, with activities as high as 14 pmol min(-1) (mg protein)(-1). The NR had a pH optimum of 9.0 while the PR had an optimum of 8.0. This study suggests that separate terminal reductases are present in strain perclace to reduce NO3(-) and ClO4(-).

    更新日期:2019-11-01
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