Screening and isolating quorum sensing inhibitor from bacteria

Abstract

Expression of virulence factors in many pathogens requires that quorum sensing autoinducer (QSA) reaches a certain threshold concentration; therefore, QSAs play central roles in the regulation of many disease processes. Quorum sensing inhibitors (QSIs) can competitively inhibit the quorum sensing signal system, which provides a novel target to combat pathogens for the development of new drugs. In this report, we used two biosensor strains, Agrobacterium tumefaciens NT1 for N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL) inhibitors and Chromobacterium violacerm CV026 for N-butanoyl-L-homoserine lactone (BHL) inhibitors, to screen for the QSIs from bacteria. There were 12 putative positive strains screened from more than 500 isolates in the initial screening. A confirmatory bioassay was carried out after concentrating the putative positive culture supernatant. Finally, three out of the twelve strains showed that one strain produced OdDHL inhibitor while the other two strains were able to inhibit BHL. Phylogenetic analysis reviewed all of these three bacterial isolates, showing that the QSA inhibition belonged to the genus Pseudomonas. We also determined the composition of microbial assemblages of the soil samples using pyrosequence date of the 16S rDNA gene, and found that the phylum Proteobacteria, to which the QSI positive isolates belong, was the most abundant in the soil of beach (56.1%), and the second in the soil from land (18.9%). This percentage was in accord with the resource of final three positive strains, two from beach and one from land. It showed an appreciable percentage of bacteria producing QSI molecules would be isolated from the soil of land and beach. Key words: Quorum sensing, quorum sensing inhibitor, screen, phylogenetic analysis.