Quorum sensing mediated virulence inhibition of an opportunistic human pathogen <i>Serratia marcescens</i> from unexplored marine sediment of Palk Bay through function driven metagenomic approach

Abstract

Indiscriminate use of antibiotics in treatment strategies of infections caused by opportunistic pathogen, <i>Serratia marcescens</i> has made the specimen multidrug resistant (MDR). The present study is focused to identify novel metaclones that selectively target quorum sensing mediated virulence factors of <i>S. marcescens</i> through culture independent approach. Metagenomic DNA library was constructed for the isolated marine sediment (Karakadu coastal region, India) metagenome using a copy control Fosmid vector. Quorum quenching activity of the cell free culture supernatants of the obtained metaclones was identified using the reduction in violacein pigment production in <i>Chromobacterium violaceum</i>. Among the obtained metagenomic clones, ethyl acetate extracts (50 µg/mL) of MCS-3 and MCS-4 showed 98 and 100 % of prodigiosin pigment reduction, respectively in <i>S. marcescens</i>. The production of secreted caseinase was reduced significantly up to 70 and 78 % when treated with 50 µg/mL ethyl acetate extracts of MCS-3 and MCS-4, respectively. Significant decrease (77 and 73 %) in lipase production was also observed with 50 µg/mL ethyl acetate extract of MCS-3 and MCS-4. This is one of the few reports that highlight the potential of function driven metagenomic approach that explicates the unexplored marine sediment of Palk Bay coastal region as a novel source of anti-QS agents.