RscS Functions Upstream of SypG To Control the syp Locus and Biofilm Formation in Vibrio fischeri
ABSTRACTTwo-component signal transduction systems, composed of sensor kinase (SK) and response regulator (RR) proteins, allow bacterial cells to adapt to changes such as environmental flux or the presence of a host. RscS is an SK required forVibrio fischerito initiate a symbiotic partnership with the Hawaiian squidEuprymna scolopes, likely due to its role in controlling the symbiosis polysaccharide (syp) genes and thus biofilm formation. To determine which RR(s) functions downstream of RscS, we performed epistasis experiments with a library of 35 RR mutants. We found that several RRs contributed to RscS-mediated biofilm formation inV. fischeri. However, only thesyp-encoded symbiosis regulator SypG was required for both biofilm phenotypes andsyptranscription induced by RscS. These data support the hypothesis that RscS functions upstream of SypG to induce biofilm formation. In addition, this work also revealed a role for thesyp-encoded RR SypE in biofilm formation. To our knowledge, no other study has used a large-scale epistasis approach to elucidate two-component signaling pathways. Therefore, this work both contributes to our understanding of regulatory pathways important for symbiotic colonization byV. fischeriand establishes a paradigm for evaluating two-component pathways in the genomics era.