Production of peptidic antimicrobials by bacterial populations from diverse coastal habitats of Goa, India

With conventional antibiotics rapidly losing their efficacy, marine microorganisms found in diverse salinity conditions are being explored for new antibacterial agents. Salinity is a major contributing factor to the distribution of biota in aquatic systems, and little is known about the production of antimicrobials by microbial communities in response to stressful environmental conditions. This work adds to the comprehension of bacterial abundance in estuarine and coastal beach waters of Goa and population structuring concerning their antimicrobial activity as specifically conferred by antimicrobial peptides. Total viable counts indicated higher bacterial load in estuarine water environments than in the higher salinity waters, suggesting a role of salinity variation as a driver of community composition in these habitats. In total, 82 bacterial isolates were selected, and the overall proteinaceous content in their exudates were screened for antimicrobial activity against Salmonella typhimurium (MTCC 91), Staphylococcus aureus (MTCC 3160), Escherichia coli (MTCC 443), Candida albicans (MTCC 227) and Aeromonas hydrophila (MTCC 1739), by the agar well diffusion method. Of these, 51.8 % showed activity against S. typhimurium, 30.3 % against S. aureus, 13.9 % against E. coli, 8.8 % against C. albicans, and 7.5 % against A. hydrophila. Compared with estuarine bacteria, those from more saline waters showed higher production of potent antimicrobial peptides, which were probably used to counter the high competition for resources. Such sites could, therefore, be potential niches for bioprospecting of microbes producing bacteriocin-like compounds.