Identification and Characterization of Cyclic Diguanylate Signaling Systems Controlling Rugosity in Vibrio cholerae

Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
Journal of bacteriology (Impact Factor: 2.81). 10/2008; 190(22):7392-405. DOI: 10.1128/JB.00564-08
Source: PubMed


Vibrio cholerae, the causative agent of the disease cholera, can generate rugose variants that have an increased capacity to form biofilms. Rugosity and biofilm formation are critical for the environmental survival and transmission of the pathogen, and these processes are controlled by cyclic diguanylate (c-di-GMP) signaling systems. c-di-GMP is produced by diguanylate cyclases (DGCs) and degraded by phosphodiesterases (PDEs). Proteins that contain GGDEF domains act as DGCs, whereas proteins that contain EAL or HD-GYP domains act as PDEs. In the V. cholerae genome there are 62 genes that are predicted to encode proteins capable of modulating the cellular c-di-GMP concentration. We previously identified two DGCs, VpvC and CdgA, that can control the switch between smooth and rugose. To identify other c-di-GMP signaling proteins involved in rugosity, we generated in-frame deletion mutants of all genes predicted to encode proteins with GGDEF and EAL domains and then searched for mutants with altered rugosity. In this study, we identified two new genes, cdgG and cdgH, involved in rugosity control. We determined that CdgH acts as a DGC and positively regulates rugosity, whereas CdgG does not have DGC activity and negatively regulates rugosity. In addition, epistasis analysis with CdgG, CdgH, and other DGCs and PDEs controlling rugosity revealed that CdgG and CdgH act in parallel with previously identified c-di-GMP signaling proteins to control rugosity in V. cholerae. We also determined that PilZ domain-containing c-di-GMP binding proteins contribute minimally to rugosity, indicating that there are additional c-di-GMP binding proteins controlling rugosity in V. cholerae.

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    • "The regulation and structure of biofilms formed under laboratory conditions has been the subject of much study and several reviews383940. It is well established that the intracellular concentration of the second messenger cyclic diguanylic acid (c-di-GMP) controls the transition between V. cholerae planktonic and biofilm lifestyles414243444546. c-di-GMP is synthesized from GTP by the activity of diguanylate cyclase (DGC) exhibiting GGDEF domains and degraded to GMP by phosphodiesterases (PDE) exhibiting EAL or HD-GYP domains [47]. "
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    • "Taken together, these findings support the notion that diverse environmental conditions modulate c-di-GMP signalling in V. cholerae. Receptors of c-di-GMP identified in V. cholerae thus far include two riboswitches, five PilZ domain proteins, biofilm regulators VpsR and VpsT, degenerate GGDEF domain containing protein CdgG, and flagellar biosynthesis regulator FlrA (Pratt et al., 2007; Beyhan et al., 2008; Sudarsan et al., 2008; Krasteva et al., 2010; Srivastava et al., 2011; 2013). While components of c-di-GMP signalling networks are being identified, molecular mechanisms by which c-di-GMP signalling operates remain unclear. "
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