Transcriptional Regulation Of Genes Encoding MFS By LysR In Vibrio Cholerae

The LysR family of transcriptional regulators represents the most abundant type of transcriptional regulator in the prokaryotic kingdom. Members of this family share a similarly sized molecule (300-350 amino acids) and have a conserved structure with an N-terminal DNA-binding helix-turn-helix motif and a C-terminal co-inducer-binding domain. Despite considerable conservation both structurally and functionally, LysR-type transcriptional regulators (LTTRs) regulate a diverse set of genes, including those involved in virulence, metabolism, quorum sensing and motility. Most LysR transcriptional regulators, while activating expression of target genes, repress their own expression, frequently by the use of divergent promoters.Vibrio cholerae, the causative agent of the acute dehydrating diarrhea disease cholera, has figured prominently in the history of infectious diseases as a cause of periodic global epidemics. Bioinformatics investigations showed that there are five special genes, encoding LysR-type transcriptional regulators in Vibrio cholerae genome, from which the downstream genes divergently transcribed and encode five MFS (major facilitator superfamily) proteins. MFS protein belongs to multidrug resistance transporter, which is responsible to export toxic compounds from within the cell envelope into the external environment, thereby decreasing the intracellular concentration of antimicrobial compounds. Here, LysR/MFS reagultion system and its effect on virulence and antimicrobial resistance were studied.To study the regulation mechanism of genes encoding MFS transporter by divergent LysR type protein, using luxCDABE as the reporter, expression detection strains were constructed. The transcriptional expression decreased significantly in lysR mutant, which indicates that these five LysR type regulators are responsible in activating the expression of genes encoding MFS. What is interesting, the production of vc1390 can interacted induce the expression of vca0083.According to western bolt assay, production of virulence factor TcpA were not effected by these five LysR type regulators. A strain lacking vca0083 was attenuated in the infant mouse model, while other lysR mutants can colonize in the intestine of infant mouse as well as wild type. Determination of the antimicrobial susceptibilities of the mutants revealed that multiple deletion of lysR/mfs strain lost resistance to tetracycline with which single lysR/mfs mutant resistant very well. We suspect that our inability to detect changes in antimicrobial susceptibility for the single mutants likely due to its phenotype being masked by the redundant efflux activity provided by other MFS in Vibrio cholerae.