Abstract

Objective: To investigate the in vitro antibacterial activity against human pathogenic bacteria and brine shrimp lethality bioassay of the marine actinobacterium. Methods: Forty six marine actinobacterial strains were isolated from sediment samples of Uppanar estuary, Cuddalore, India. Preliminary screening was done by cross-streak method and the potential strain was identified by morphological, chemotaxonomical and molecular methods. Fermentation was done and the metabolite was obtained by liquid-liquid extraction using ethyl acetate and purified by silica gel (100-200 mesh) column chromatography. The purified metabolite was tested for antibacterial activity, minimal inhibitory concentration and brine shrimp lethality bioassay. Results: Among the forty six strains, CAS72 was found effective against human pathogenic bacteria. The strain CAS72 was identified as Streptomyces sp. The purified metabolite exhibited a significant in vitro antibacterial activity. The MIC value was also determined against human pathogenic bacteria and a strong cytotoxic activity in brine shrimp lethality assay was observed and the LC 50 value was 23.5 µg/mL. Conclusions: The present investigation reveals that the marine actinobacteria are well obtainable in Uppanar estuary environment and it can provide a definite source for novel bioactive metabolites.

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