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

Indiscriminate use of antibiotics in treatment strategies of infections caused by opportunistic pathogen, Serratia marcescens 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 S. marcescens 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 Chromobacterium violaceum. 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 S. marcescens. 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.