Marine Biotechnology Division, Central Marine Fisheries Research Institute, Ernakulam North, P.B. No. 1603, Cochin, India.
Faculty of Marine Sciences, Lakeside Campus, Cochin University of Science and Technology, Cochin, Kerala, India.
Arch Microbiol. 2020 May;202(4):905-920. doi: 10.1007/s00203-019-01800-2. Epub 2020 Jan 2.
The development of drug-resistant bacteria and the necessity for unique antimicrobial agents, directed to the search of new habitats to screen the production of anti-infective substances. Culture-dependent studies of heterotrophic bacteria from the intertidal macroalgae thriving along the Southern coast of India resulted in the isolation of 148 strains, which were assayed for antibacterial activities against wide spectrum of pathogens including drug-resistant pathogens, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecalis (VRE). Two of the most active strains with a zone of inhibition ≥ 30 mm on spot over lawn assay, belonging to the phyla Firmicutes and Gamma-proteobacteria, isolated from a Rhodophycean marine macroalga, Hypnea valentiae, were selected for bioprospecting studies. They were further characterized as Shewanella algae MTCC 12715 and Bacillus amyloliquefaciens MTCC 12716, based on integrated phenotypic and genotypic analysis. The bacterial extracts exhibited significant antibacterial activities against MRSA and VRE with minimum inhibitory concentrations of 6.25-12.5 µg/mL. Time kill kinetic profiles of these bacteria revealed rapid bactericidal activity against both MRSA and E. coli, showing a ≥ 3log decline in viable cell count compared to the initial. In BacLight™ live/dead staining technique, the propidium iodide uptake results appropriately attributed that the components in the B. amyloliquefaciens extract might compromise the integrity of the cytoplasmic membrane of the pathogenic bacteria. Type-1 pks gene (MH157093) of S. algae and hybrid nrps/pks gene (MH157092) of B. amyloliquefaciens could be amplified. Antibacterial activity study combined with the results of amplified genes coding for polyketide synthase and nonribosomal peptide synthetase showed that these marine symbiotic bacteria had a promising broad-spectrum activity, and therefore, could be used against the emerging dilemma of antibiotic-resistant bacterial infections.
耐药菌的发展和对独特抗菌剂的需求促使人们到新的栖息地寻找抗感染物质。对印度南部沿海潮间带大型藻类中异养细菌的培养依赖性研究导致分离出 148 株菌株，这些菌株对抗广泛病原体的抗菌活性进行了测定，包括耐药病原体、耐甲氧西林金黄色葡萄球菌 (MRSA) 和万古霉素耐药粪肠球菌 (VRE)。在斑点过生长法中，有 2 株具有抑制圈≥30mm 的最活跃菌株，属于厚壁菌门和γ-变形菌门，从红藻门海洋大型藻类 Hypnea valentiae 中分离出来，被选中进行生物勘探研究。根据综合表型和基因型分析，它们进一步被鉴定为 Shewanella algae MTCC 12715 和 Bacillus amyloliquefaciens MTCC 12716。细菌提取物对 MRSA 和 VRE 表现出显著的抗菌活性，最低抑菌浓度为 6.25-12.5μg/ml。这些细菌的时间杀伤动力学曲线显示，它们对 MRSA 和大肠杆菌具有快速杀菌活性，与初始值相比，活菌数下降了≥3log。在 BacLight™活菌/死菌染色技术中，碘化丙啶摄取结果恰当地表明，B. amyloliquefaciens 提取物中的成分可能破坏了致病性细菌的细胞质膜完整性。可以扩增到 S. algae 的 Type-1 pks 基因 (MH157093) 和 B. amyloliquefaciens 的 hybrid nrps/pks 基因 (MH157092)。抗菌活性研究结合扩增基因编码聚酮合酶和非核糖体肽合酶的结果表明，这些海洋共生细菌具有广谱的活性，因此可以用于对抗抗生素耐药细菌感染这一新兴难题。
