ABSTRACT
In Vibrio cholerae, the second messenger
3′,5′-cyclic diguanylic acid (c-di-GMP) regulates
several cellular processes, such as formation of corrugated colony
morphology, biofilm formation, motility, and virulence factor
production. Both synthesis and degradation of c-di-GMP in the cell are
modulated by proteins containing GGDEF and/or EAL domains, which
function as a diguanylate cyclase and a phosphodiesterase,
respectively. The expression of two genes, cdgC and
mbaA, which encode proteins harboring both GGDEF and EAL
domains is higher in the rugose phase variant of V. cholerae
than in the smooth variant. In this study, we carried out gene
expression analysis to determine the genes regulated by CdgC in the
rugose and smooth phase variants of V. cholerae. We determined
that CdgC regulates expression of genes required for V.
cholerae polysaccharide synthesis and of the transcriptional
regulator genes vpsR, vpsT, and hapR. CdgC
also regulates expression of genes involved in extracellular protein
secretion, flagellar biosynthesis, and virulence factor production. We
then compared the genes regulated by CdgC and by MbaA, during both
exponential and stationary phases of growth, to elucidate processes
regulated by them. Identification of the regulons of CdgC and MbaA
revealed that the regulons overlap, but the timing of regulation
exerted by CdgC and MbaA is different, suggesting the interplay and
complexity of the c-di-GMP signal transduction pathways operating in
V.
cholerae.