C-di-GMP Regulates Motile to Sessile Transition by Modulating MshA Pili Biogenesis and Near-Surface Motility Behavior in <i>Vibrio cholerae</i>

<div><p>In many bacteria, including <i>Vibrio cholerae</i>, cyclic dimeric guanosine monophosphate (c-di-GMP) controls the motile to biofilm life style switch. Yet, little is known about how this occurs. In this study, we report that changes in c-di-GMP concentration impact the biosynthesis of the MshA pili, resulting in altered motility and biofilm phenotypes in <i>V</i>. <i>cholerae</i>. Previously, we reported that <i>cdgJ</i> encodes a c-di-GMP phosphodiesterase and a Δ<i>cdgJ</i> mutant has reduced motility and enhanced biofilm formation. Here we show that loss of the genes required for the mannose<i>-</i>sensitive hemagglutinin <i>(</i>MshA<i>)</i> pilus biogenesis restores motility in the Δ<i>cdgJ</i> mutant. Mutations of the predicted ATPase proteins <i>mshE</i> or <i>pilT</i>, responsible for polymerizing and depolymerizing MshA pili, impair near surface motility behavior and initial surface attachment dynamics. A Δ<i>cdgJ</i> mutant has enhanced surface attachment, while the Δ<i>cdgJmshA</i> mutant phenocopies the high motility and low attachment phenotypes observed in a Δ<i>mshA</i> strain. Elevated concentrations of c-di-GMP enhance surface MshA pilus production. MshE, but not PilT binds c-di-GMP directly, establishing a mechanism for c-di-GMP signaling input in MshA pilus production. Collectively, our results suggest that the dynamic nature of the MshA pilus established by the assembly and disassembly of pilin subunits is essential for transition from the motile to sessile lifestyle and that c-di-GMP affects MshA pilus assembly and function through direct interactions with the MshE ATPase.</p>