Project description:Vibrio campbellii BB120 (ATCC BAA-1116, previously designated as Vibrio harveyi) is a fundamental model strain for studying population density-based cell-to-cell communication, known as quorum sensing, among gram-negative bacteria. In V. campbellii BB120, sensing of autoinducers at high cell densities activates the expression of the master transcriptional regulator, LuxR, which controls the expression of genes involved in group behaviors. Unlike BB120, the Vibrio campbellii environmental isolate DS40M4 was recently shown to be capable of natural transformation, a process by which bacteria take up exogenous DNA and incorporate it into their genome via homologous recombination. Here, we compare other phenotypes between DS40M4 and BB120. We find that DS40M4 has a faster growth rate and stronger type VI secretion-mediated cell killing, whereas BB120 forms more robust biofilms and is bioluminescent. We exploited the power of natural transformation to rapidly generate >30 mutant strains to explore the function of DS40M4-encoded homologs of the BB120 quorum-sensing system. Our results show that DS40M4 has a similar quorum-sensing circuit to BB120 but with three distinct differences: 1) DS40M4 lacks the canonical HAI-1 autoinducer LuxM synthase but has an active LuxN receptor, 2) the quorum regulatory small RNAs (Qrrs) are not solely regulated by autoinducer signaling through the response regulator LuxO, and 3) the DS40M4 LuxR regulon is <100 genes, which is relatively small compared to the >400 genes regulated in BB120. This work illustrates that DS40M4 is a tractable and relevant model strain for studying quorum-sensing phenotypes in Vibrio campbellii.
Project description:Vibrio campbellii BAA-1116 was used as a Harveyi clade model organism to determine the impact of indole signaling on virulence. Gene expression analysis of V. campbellii grown in LB35 broth with or without 100 μM indole revealed that indole decreased: (1) V. campbellii virulence in shrimp and prawn challenge assays, (2) exopolysaccharide production, and (3) swimming motility. The results also indicated that indole inhibits quorum sensing-regulated bioluminescence and blocks the three-channel quorum sensing system by interfering with quorum sensing signal transduction.