PHENOTYPIC AND COMPARATIVE ANALYSIS OF QUORUM SENSING MUTANTS IN VIBRIO PARAHAEMOLYTICUS

Abstract

Quorum sensing is a type of bacterial cell-to-cell communication process using extracellular signaling molecules called autoinducers that reflect cell density. Bacteria respond to these autoinducers to detect changes in cell population and therefore alter gene expression. Vibrio parahaemolyticus is an enteric pathogen that causes gastroenteritis when consumed through raw or undercooked shellfish. We used V. parahaemolyticus as our model organism to study the quorum sensing pathway. In the V. parahaemolyticus quorum sensing pathway, at low cell density, quorum sensing response regulator LuxO is phosphorylated and activates sigma factor 54, also known as RpoN. Activated RpoN recruits RNA polymerase to initiate transcription of the five small quorum regulatory RNAs (qrr1-qrr5). The Qrr sRNAs post-transcriptionally stabilize aphA and degrade opaR mRNA transcripts. OpaR is the quorum sensing high cell density master regulator that has previously been shown to positively regulate the virulence factor capsule polysaccharide (CPS). We investigated the role of the Qrr sRNAs in CPS production, swimming, and swarming motility. We examined six strains: wild type, ΔopaR, Δqrr null (no qrrs), Δqrr1,3,4,5, Δqrr1,2,3,5 and Δqrr1,2,3,4, and determined that the Δqrr1,3,4,5 mutant restored the expression of wild type CPS, swimming and swarming. This indicates that qrr2 alone is capable of controlling the quorum sensing response in V. parahaemolyticus