Quorum sensing in thermophiles characterization of autoinducer 2 system in meiothermus ruber and thermus thermophilus Its inhibition and application in pulp and paper industry

Abstract

Quorum sensing (QS) is a cell-to-cell communication process used by bacteria to regulate gene expression in response to cell density of the overall bacterial population. In mesophilic bacteria, QS regulates myriad processes such as bioluminescence, biofilm formation, motility, virulence, regulation of stress related genes and antibiotic resistance. Despite the vast information available regarding QS in mesophiles, the communication mechanisms in thermophiles are largely unknown, although the processes like formation of biofilms by thermophilic bacteria and archaea are well recognized. This study has aimed at exploring the existence and nature of QS systems in 106 thermophilic eubacteria and 21thermophilic archaea through in-silico analysis, where it was found that AI-2 might be a system of communication. Further, the role of QS (biofilm, motility and efflux pump regulation) was explored in Meiothermus ruber and Thermus thermophilus, responsible for deterioration of paper in paper industry by complementation of their luxS (autoinducer-2 synthase) in luxS- deletion mutant E.coli BW30044. Transcriptome analysis showed the presence of 204 significantly differentially regulated genes between E. coli BW30044/pGEM-T-luxS Mr and E. coli BW30044 after complementation of luxS. Quorum quenching was done using natural and synthetic compounds (silymarin, quercetin, palmitic acid, methional and compound X) by targeting the LuxS, as several dominant bacteria, regarded as early colonizers involved in slime production in paper-mills, produce AI-2 signal. Compound X was found to be the most effective inhibitor as it reduces the biofilm of consortium of paper-mill isolates to 50% at concentration 23.43and#956;g/ml while acted as a biocide at 30and#956;g/ml concentration.