Antimicrobial compounds produced by Streptomyces sp. VITGV01 against selected human pathogens

Abstract

Streptomyces are well known to produce a large number of diverse compounds. An endophytic actinomycete, Streptomyces sp. VITGV01 was isolated from a farm tomato plant. Isolated actinomycetes are cultured in ISP2 medium supplemented with nystatin (15μg/ml) and nalidixic acid (50μg/ml). A total of 240 actinomycetes were isolated and 77 showed antimicrobial properties. One strain that exhibited a high zone of inhibition on primary screening was selected (VITGV01). The SEM studies revealed filamentous tubular structures with continuous aerial hyphae differentiated into tiny, smooth-surfaced chainlike spores. Based on the 16S rRNA analysis and physiological tests, this isolate was found to be a member of the genus Streptomyces suggesting that it might be a new sp. Maximum biomass production was recorded in media containing 1% sucrose and 1% yeast extract cultured at pH 7.0 for 15 days at 300C. The secondary metabolites were active against Bacillus subtilis (MTCC 2756), Staphylococcus aureus (MTCC 737), Escherichia coli (MTCC 1687) and Klebsiella pneumoniae (MTCC 109). A maximum zone of inhibition was observed against K. pneumoniae (22 mm) and a minimal zone of inhibition against B. subtilis (8 mm). FTIR analysis revealed amine, alkane (C=C) aromatic ring, secondary alcohol and alkyl halide groups. The GCMS data showed twenty different compounds, of which fifteen are antimicrobial.