Antimicrobial properties of cultivable bacteria associated with seaweeds in the Gulf of Mannar on the southeast coast of India

Abstract

In this study, 234 bacterial strains were isolated from 7 seaweed species in the Gulf of Mannar on the southeast coast of India. The strains having consistent antimicrobial activity were chosen for further studies, and this constituted about 9.8% of the active strains isolated. Phylogenetic analysis using 16S rDNA sequencing with the help of classical biochemical identification indicated the existence of 2 major phyla, Firmicutes and Proteobacteria. Antimicrobial activity analysis combined with the results of amplifying genes encoding for polyketide synthetase and nonribosomal peptide synthetase showed that seaweed-associated bacteria had broad-spectrum antimicrobial activity. These epibionts might be beneficial to seaweeds by limiting or preventing the development of competing or fouling bacteria. Phylogenetic analysis of ketosynthase (KS) regions with respect to the diverse range of KS domains showed that the KS domains from the candidate isolates were of Type I. The bacterial cultures retained their antimicrobial activities after plasmid curing, which further suggested that the antimicrobial activity of these isolates was not encoded by plasmid, and the genes encoding the antimicrobial product might be present within the genome. Seaweed-associated bacteria with potential antimicrobial activity suggested that the seaweed species are an ideal ecological niche harboring specific bacterial diversity representing a largely underexplored source of antimicrobial secondary metabolites.

Antibacterial aryl-crowned polyketide from Bacillus subtilis associated with seaweed Anthophycus longifolius

“…; Thilakan et al . ). The exploitation of this symbiotic microbiota for antibacterial metabolite discovery is an attractive area of research (Gomez et al .…”

“…; Thilakan et al . ). The present research report likewise recognized the principles of pks‐ 1 gene encrypted aryl‐crowned macolactin as a secondary metabolite of B. subtilis MTCC 10403.…”

“…; Thilakan et al . ). The chemicals used in this study were acquired from E‐Merck (E‐Merck, Darmstadt, Germany) and were of analytical grade.…”

“…The seaweed‐associated bacterial strains were isolated by a previously described method (Thilakan et al . ) and assessed for their antimicrobial characteristics against Vibrio parahemolyticus ATCC ® 17802 ™ , V. parahaemolyticus MTCC 451, Vibrio vulnificus MTCC 1145, A. hydrophilla MTCC 646, Vibrio harveyi MTCC 3438, Vibrio alginolyticus MTCC 4439, Escherichia coli MTCC 1303, Klebsiella pneumoniae MTCC 109, Pseudomonas aeruginosa MTCC 429, Salmonella enterica serotype Typhi MTCC 733, by spot‐over lawn experiment (Chakraborty et al . ).…”

“…Seaweeds and their associated bacterial communities are potential sources in the field of functional food and biotechnology due to their abilities to produce diverse groups of compounds with a broad range of bioactivities (Zubia et al 2009;Chakraborty et al 2016;Le Lann et al 2016;Thilakan et al 2016). Among different species of marine bacteria, Bacillus sp.…”