Phylogenetic-affiliation, antimicrobial potential and PKS gene sequence analysis of moderately halophilic Streptomyces sp. inhabiting an Indian saltpan

Abstract

A Gram-positive, moderately halophilic Streptomyces strain, designated JAJ06, was isolated from saltpan soil collected at Tuticorin, India, and subjected to a polyphasic characterization with an insight into their biotechnological importance. Growth characteristics and antimicrobial com-pound producing capabilities of Streptomyces sp. JAJ06 were observed on various International Streptomyces Project (ISP) media and production media. Optimum growth was observed on modified ISP 4 medium supplemented with 4% NaCl (w/v) at 29 °C incubated for 7 days. Maximum antibacterial compound production with good mycelial growth was observed on starch-yeast extract-peptone medium prepared with seawater (90%, v/v). The 16S rRNA gene based phylogenetic affiliation was determined by using various bioinformatics tools and the strain was identified as Streptomyces sp. JAJ06 with 99% sequence similarity to Streptomyces radiopugnans(T) . An antimicrobial assay of antimicrobial compound derived from Streptomyces sp. JAJ06 against a set of bacteria and a yeast strain revealed antimicrobial activity with significant minimal inhibitory concentrations. The potential antimicrobial compound produced by Streptomyces sp. JAJ06 was found to be polyketide in nature. Cloning and sequence analysis of 613-bp fragment of ketosynthase gene from the type-II polyketide operon revealed that Streptomyces sp. JAJ06 has the KSα gene with 91% sequence similarity to the type II polyketide synthase gene of Streptomyces peucetius.