Antagonistic activity of Bacillus amyloliquefaciens subsp. amyloliquefaciens against multidrug resistant Serratia rubidaea

Serratia rubidaea is an opportunistic Gram-negative pathogen that has developed antimicrobial resistance to a variety of commercial antibiotics. The spread of this multidrug-resistant pattern predicts that it will get harder and harder to treat S. rubidaea infections in the future. For this perception, antimicrobial proteins might represent a safe, effective, and biodegradable alternative because their site of action is on cyclic peptides. In this study, one candidate Bacillus amyloliquefaciens subsp. amyloliquefaciens was isolated from the soil of Sundarban mangrove forest, and its identification was confirmed both using the PCR (Polymerase chain reaction) method and the BIOLOG™ microbial identification system. The antibacterial protein, which has a molecular mass of about 50 kDa, was isolated from B. amyloliquefaciens subsp. amyloliquefaciens. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was used to confirm the extracted protein's purity. This potential protein was discovered to develop and exhibit antagonistic activity throughout a broad temperature, pH, and salinity range. At doses ranging from 300 to 400 μg/ml, this protein has antagonistic activity against multidrug resistant S. rubidaea and a wide range of other resistant pathogenic bacteria such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and so on. The research provides new insights to develop bio-control agents that can be applied for prevent, treat, and control infectious diseases caused by multidrug resistant S. rubidaea, as well as other pathogenic bacteria.

深红沙雷菌（Serratia rubidaea）是一种机会致病性革兰氏阴性病原菌，已对多种商用抗生素产生抗菌耐药性。该多重耐药表型的传播预示着，未来治疗深红沙雷菌感染的难度将与日俱增。鉴于此，抗菌蛋白或许代表了一种安全、有效且可生物降解的替代方案，因其作用靶点为环肽。本研究从孙德尔本斯（Sundarban）红树林土壤中分离得到一株候选解淀粉芽孢杆菌解淀粉亚种（Bacillus amyloliquefaciens subsp. amyloliquefaciens），并通过聚合酶链式反应（PCR，Polymerase chain reaction）法与BIOLOG™微生物鉴定系统完成了菌株鉴定。从该解淀粉芽孢杆菌解淀粉亚种中分离得到一种分子量约为50 kDa的抗菌蛋白，采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE，Sodium dodecyl-sulfate polyacrylamide gel electrophoresis）对提取所得蛋白的纯度进行了验证。研究发现，该潜在蛋白可在宽泛的温度、pH值及盐度范围内展现拮抗活性。在300至400 μg/ml的剂量范围内，该蛋白对多重耐药的深红沙雷菌，以及大肠杆菌（Escherichia coli）、金黄色葡萄球菌（Staphylococcus aureus）、铜绿假单胞菌（Pseudomonas aeruginosa）等多种耐药致病菌均具有拮抗活性。本研究为开发可用于预防、治疗及控制由多重耐药深红沙雷菌及其他致病菌引发的感染性疾病的生物防治制剂提供了全新视角。