Increased prevalence of microbial resistance and development of drug-resistant pathogens have triggered an urge among researchers to discover potential antimicrobial compounds, particularly from the marine habitat. The present study highlights the cultivable diversity and bioactivities of heterotrophic bacteria associated with marine macroalgae of southeast Indian coastal region. Culture-dependent isolation method resulted in 40 isolates, in which greater part of the isolates represented Gammaproteobacteria (62%) followed by that comprised of the phylum Firmicutes. One of the most active strains isolated from a macroalga, Laurencia papillosa, was characterized based on the integrated phenotypic and genotypic analysis as Bacillus velezensis MBTDLP1 MTCC 13048, with an inhibition zone of about 35 mm against methicillin-resistant Staphylococcus aureus (MRSA), was selected for bioprospecting studies. Type-I pks gene (MT394492) of 700 bp could be amplified from the heterotrophic B. velezensis. The bacterium exhibited siderophore production and possessed genes implicated in the biosynthesis of siderophore type of metabolites exhibiting 99% similarity with other GenBank sequences in BLAST search. B. velezensis exhibited promising anti-infective properties against methicillin-resistant Staphylococcus aureus (minimum inhibitory concentration 15 µg/mL), and the activities were positively correlated (r2 > 0.9) with iron-chelating activities. Chemical investigation of the organic extract of B. velezensis MBTDLP1 characterized a macrocyclic polyketide exhibiting prospective antibacterial potential against methicillin-resistant S. aureus (MIC 0.38 µg/mL), than that exhibited by positive control chloramphenicol (6.25 µg/mL). Significant antibacterial activity against drug-resistant bacteria combined with the presence of genes coding for bioactive secondary metabolites revealed that this marine symbiotic bacterium could be used against emerging antibiotic resistance.

中文翻译：

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海洋巨藻相关的异养芽孢杆菌：一种新型抗菌剂，具有铁载体作用模式，可抵抗耐药的院内病原体。

微生物耐药性的增加和耐药病原体的发展引发了研究人员发现潜在抗菌化合物的冲动，特别是来自海洋栖息地的化合物。本研究强调了与印度东南部沿海地区海洋大型藻类相关的异养细菌的可培养多样性和生物活性。培养依赖性分离方法产生了 40 个分离株，其中大部分分离株代表 Gammaproteobacteria (62%)，其次是厚壁菌门。从大型藻类 Laurencia papillosa 中分离出的最活跃的菌株之一基于综合表型和基因型分析被表征为 Bacillus velezensis MBTDLP1 MTCC 13048，对耐甲氧西林金黄色葡萄球菌 (MRSA) 具有约 35 mm 的抑菌圈，被选择用于生物勘探研究。700 bp 的 I 型 pks 基因 (MT394492) 可以从异养的 B. velezensis 中扩增出来。该细菌表现出铁载体的产生，并拥有与铁载体类型代谢物的生物合成有关的基因，在 BLAST 搜索中与其他 GenBank 序列具有 99% 的相似性。B. velezensis 对耐甲氧西林金黄色葡萄球菌（最低抑制浓度 15 µg/mL）表现出良好的抗感染特性，并且活性与铁螯合活性呈正相关 (r2 > 0.9)。B. 有机提取物的化学研究 velezensis MBTDLP1 表征了一种大环聚酮化合物，与阳性对照氯霉素 (6.25 µg/mL) 相比，它对耐甲氧西林金黄色葡萄球菌（MIC 0.38 µg/mL）具有潜在的抗菌潜力。对耐药细菌的显着抗菌活性与编码生物活性次生代谢产物的基因的存在相结合表明，这种海洋共生细菌可用于对抗新出现的抗生素耐药性。