The putative oligosaccharide translocase SypK connects biofilm formation with quorum signaling in Vibrio fischeri.
Bottom Line: We found that overexpression of sypK, which encodes a putative oligosaccharide translocase, is sufficient to activate qrr1, and, in addition, this effect appears to depend on the kinase activity of the sensor LuxQ.Finally, we found that induction of the syp locus by overexpression of sypG was sufficient to activate qrr1 levels.Together, our results show how conditions that promote biofilm formation impact the quorum-signaling network in V. fischeri, and further highlight the integrated nature of the regulatory circuits involved in complex bacterial behaviors.
Affiliation: Department of Biochemistry and Molecular Biology, Eberly College of Science, The Pennsylvania State University, University Park, Pennsylvania, 16802; Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, 53706.Show MeSH
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Mentions: We first examined the response of qrr1 expression to sypK induction in the absence of either LuxO or LuxU, which are the phosphorelay proteins that directly control qrr1 expression (Fig. 1). We found that qrr1 expression remained at or lower than the wild-type level in either ΔluxO or ΔluxU mutants, regardless of whether sypK was induced (Fig. 6), indicating that both proteins are required for SypK-dependent activation of qrr1. We next examined qrr1 expression in a strain containing a luxOD47E allele, which expresses a variant of LuxO that mimics the phosphorylated state of LuxO (Lupp and Ruby 2005). We found that the level of qrr1 expression in the luxOD47E mutant was higher than in wild-type cells (Fig. 6). Importantly, qrr1 expression in the luxOD47E mutant was independent of sypK induction, suggesting that an intact LuxU-LuxO phosphorelay is required for SypK to increase qrr1 expression (Fig. 6). Together, these results indicate that SypK acts upstream of the LuxU-LuxO phosphorelay to affect qrr1 expression.
Affiliation: Department of Biochemistry and Molecular Biology, Eberly College of Science, The Pennsylvania State University, University Park, Pennsylvania, 16802; Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, 53706.