Identification and analysis of antimicrobial biosynthetic genes in marine microbial symbionts

Abstract

Contagious spread of drug resistant strains as well as newer diseases necessitates the development of novel antibacterial agents which led scientists to explore new niches like marine habitat and associated marine microbes. Therefore, the present study aimed to check whether the microbes associated with unexplored marine invertebrates namely, P. viridis, C. feriatus, P. pelagicus, P. sanguinolentus and S. olivacea have antimicrobial activity against human and aquatic pathogens including some MDR (Multi Drug Resistant) strains. Additionally, antimicrobial biosynthetic genes namely, NRPS (Non ribosomal peptide synthetase) and PKS (Polyketide synthase) associated with the positive isolates was isolated and analyzed. Out of 123 isolates screened against 12 indicator pathogens, 27 isolates showed antibacterial activity and the isolates with maximum activities were identified as Staphylococcus pasteuri and Pseudomonas aeruginosa. When these isolates were screened for the presence of NRPS and PKS genes, 9, 2 and 4 of them showed the presence of NRPS, PKS and both NRPS and PKS genes respectively. A non-parametric statistical analysis using Mann Whitney U test showed that the presence of NRPS/PKS gene has statistically significant influence on the total activity scores (p<0.05) and the scores was statistically significantly higher in NRPS/PKS positive isolates than the negative isolates. Detailed in-silico analysis of these amplicons to predict their activity, revealed two new NRPS ‘A’ domain binding signature and detected 4 antagonistic microbes with previously uncharacterized NRPS products from the marine crab haemolymph associated bacterial collections. The present study successfully generated NRPS gene sequences from four antagonistic bacterial species for which information of NRPS ‘A’ domain was not available earlier. Altogether, the study supports the hypothesis stating that marine invertebrate bacterial associations can provide strains having future biotechnological and pharmaceutical applications in aquaculture industry.