LuxU connects quorum sensing to biofilm formation in V ibrio fischeri

Summary Biofilm formation by V ibrio fischeri is a complex process involving multiple regulators, including the sensor kinase ( SK ) RscS and the response regulator ( RR ) SypG , which control the sy mbiosis p olysaccharide ( syp ) locus. To identify other regulators of biofilm formation in V . fischeri , we screened a transposon library for mutants defective in wrinkled colony formation. We identified LuxQ as a positive regulator of syp ‐dependent biofilm formation. LuxQ is a member of the L ux phosphorelay and is predicted to control bioluminescence in concert with the SK AinR , the phosphotransferase LuxU and the RR LuxO . Of these, LuxU was the only other regulator that exerted a substantial impact on biofilm formation. We propose a model in which the L ux pathway branches at LuxU to control both bioluminescence and biofilm formation. Furthermore, our evidence suggests that LuxU functions to regulate syp transcription, likely by controlling SypG activity. Finally, we found that, in contrast to its predicted function, the SK AinR has little impact on bioluminescence under our conditions. Thus, this study reveals a novel connection between the L ux and S yp pathways in V . fischeri , and furthers our understanding of how the L ux pathway regulates bioluminescence in this organism.