Quorum sensing regulators are required for metabolic fitness in Vibrio parahaemolyticus

Date
2017-01-09
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American Society for Microbiology
Abstract
Quorum sensing (QS) is a process by which bacteria alter gene expression in response to cell density changes. In Vibrio species, at low cell density, the sigma 54-dependent response regulator LuxO, is active, and regulates the two QS master regulators AphA, which is induced and OpaR, which is repressed. At high cell density the opposite occurs, LuxO is inactive, therefore OpaR is induced and AphA is repressed. In V. parahaemolyticus, a significant enteric pathogen of humans, the role of these regulators in pathogenesis is less known. We examined deletion mutants of luxO, opaR and aphA for in vivo fitness using an adult mouse model. We found that the luxO and aphA mutants were defective in colonization compared to wild-type. The opaR mutant did not show any defect in vivo. Colonization was restored to wild-type levels in a luxO/opaR double mutant and was also increased in an opaR/aphA double mutant. These data suggest that AphA is important and that overexpression of opaR is detrimental to in vivo fitness. RNA-seq analysis of the wild-type and luxO mutant grown in mouse intestinal mucus showed that 60% of the genes that were downregulated in the luxO mutant were involved in amino acid and sugar transport and metabolism. These data suggest that the luxO mutant has a metabolic disadvantage, which was confirmed by growth pattern analysis using phenotype microarrays. Bioinformatics analysis revealed OpaR binding sites in the regulatory region of 55 carbon transporter and metabolism genes. Biochemical analysis of five representatives of these regulatory regions demonstrated direct binding of OpaR in all five tested. These data demonstrate the role of OpaR in carbon utilization and metabolic fitness, an overlooked role in the QS regulon.
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Citation
Kalburge, S., Carpenter, M., Rozovsky, S., & Boyd, E. (2017). Quorum Sensing Regulators Are Required for Metabolic Fitness in Vibrio parahaemolyticus. Infection And Immunity, 85(3), e00930-16. http://dx.doi.org/10.1128/iai.00930-16