Department of Zoology, Alagappa Govt. Arts College, Karaikudi, 630 004, Tamil Nadu, India; Department of Animal Health Management, Science Campus, Alagappa University, Karaikudi, 630 004, Tamil Nadu, India.
Marine Biotechnology Laboratory, Department of Biotechnology, Sri Kaliswari College (Autonomous), Sivakasi, 623 130, Virudhunagar District, Tamilnadu, India.
Microb Pathog. 2019 Sep;134:103597. doi: 10.1016/j.micpath.2019.103597. Epub 2019 Jun 12.
The present study probed the antimicrobial potential of a rare mangrove associated actinomycetes against an array of aquatic bacterial pathogens causing disease outbreak in fin and shellfish. Antibacterial activity results implied that the mangrove associated actinomycetes RAS7 exhibited striking inhibitory activity against the tested aquatic bacterial pathogens. Identification of strain RAS7 through polyphasic and 16S rRNA sequencing affirmed that the strain belongs to Rhodococcus sp. Optimization of culture conditions for antibacterial activity by Rhodococcus sp. inferred that it grew well and exerted notable antagonistic activity in medium supplied with 1% galactose and peptone as carbon and nitrogen sources. Similarly, the strain grown in 0.1% tyrosine, 1% NaCl, pH 7.5 and temperature 35 °C recorded maximum bioactivity against the test pathogens. The crude ethyl acetate extract of Rhodococcus sp. at 200 μg/ml recorded markedly pronounced growth inhibitory activity ranged between 14 and 29 mm. The cytotoxic effect of crude extract against brine shrimp Artemia salina nauplii registered LC value of 134.294 μg/ml after 24 h of exposure. The secondary metabolite was separated using Ethyl acetate: Methanol (7:3) as solvent system through TLC. The TLC autobiogram mapped the active spot in TLC with Rf value of 0.84. Analysis of chemical constituents and FT-IR spectral analysis substantiated that the active principle in bioassay guided fraction was sterol-glycosides.
本研究探讨了一种稀有红树林相关放线菌对一系列引起鱼类和贝类疾病爆发的水生细菌病原体的抗菌潜力。抗菌活性结果表明，红树林相关放线菌 RAS7 对测试的水生细菌病原体表现出显著的抑制活性。通过多相和 16S rRNA 测序对菌株 RAS7 进行鉴定，证实该菌株属于 Rhodococcus sp. 通过 Rhodococcus sp. 对抗菌活性的培养条件进行优化，推断其在含有 1%半乳糖和蛋白胨作为碳源和氮源的培养基中生长良好，并表现出显著的拮抗活性。同样，在 0.1%酪氨酸、1%NaCl、pH7.5 和 35°C 温度下生长的菌株对测试病原体的生物活性最高。Rhodococcus sp. 的粗乙酸乙酯提取物在 200 μg/ml 时记录到显著的生长抑制活性，范围在 14 到 29 mm 之间。粗提取物对盐水虾 Artemia salina 无节幼体的细胞毒性作用在暴露 24 小时后记录到 LC 值为 134.294 μg/ml。次生代谢物通过 TLC 用乙酸乙酯：甲醇（7:3）作为溶剂系统进行分离。TLC 自传图在 TLC 中绘制了活性斑点，其 Rf 值为 0.84。化学成分分析和 FT-IR 光谱分析证实，生物测定导向馏分中的活性成分是甾醇糖苷。
