Screening and characterization of antagonistic Streptomyces sp. JS20 from marine sediment in Vaan Island

In the present study, we have isolated twenty four different Actinomycetia strains from marine sediment in Vaan island, Tuticorin district (8.83639°N/78.21047°E), Tamil Nadu, India. Among these, the isolate JS20 has been identified as Streptomyces sp. JS20 by 16 s rRNA phylogenetic analysis, which exhibited prominent antibacterial activity against panel of WHO priority pathogens mostly, MRSA a clinical pathogen. The bioassay guided fractionation dependent active compound exhibits RT at 3.0 with maximum UV absorption of 250 nm. Furthermore, FT-IR, 1H NMR, 13C NMR and LC-MS spectral analysis confirms the existence of polyketide metabolites with molecular mass of m/z 380.74 M+Na+ and m/z 397.00 M+K+ adducts. Minimum Inhibitory Concentration (MIC) and Minimum Bacterial Concentration (MBC) value of the purified compound against MRSA was found to be 7.81 µg/ml and 125 µg/ml respectively. Additionally, the anti-MRSA campaign of the purified compound was upheld qualitatively using the high content screening (HCS) and quantitatively by Flow Cytometry (FACS) analysis which indicates concentration of bactericidal activity increases when the concentration of the purified compound was increased. The action of bioactive compound was determined by cell morphology disruption on MRSA bacterial cells as results, the cytoplasm cellular contents and ATP leaky were ahead. Apart from these studies, NaCl tolerant, the multiple passage studies and post antibiotic effect of bioactive compound has been evaluated against the MRSA. Hence, the study revealed that the bioactive compound from the Streptomyces sp. JS20 can be used as a lead compound to inhibit the MRSA in future.