The cyclic AMP receptor protein modulates colonial morphology in Vibrio cholerae.
Inactivation of the quorum-sensing regulator HapR causes Vibrio cholerae El Tor biotype strain C7258 to adopt a rugose colonial morphology that correlates with enhanced biofilm formation. V. cholerae mutants lacking the cyclic AMP (cAMP) receptor protein (CRP) produce very little HapR, which results in elevated expression of Vibrio exopolysaccharide (vps) genes and biofilm compared to the wild type. However, Deltacrp mutants still exhibited smooth colonial morphology and expressed reduced levels of vps genes compared to isogenic hapR mutants. In this study we demonstrate that deletion of crp and cya (adenylate cyclase) converts a rugose DeltahapR mutant to a smooth one. The smooth DeltahapR Deltacrp and DeltahapR Deltacya double mutants could be converted back to rugose by complementation with crp and cya, respectively. CRP was found to enhance the expression of VpsR, a strong activator of vps expression, but to diminish transcription of VpsT. Ectopic expression of VpsR in smooth DeltahapR Deltacrp and DeltahapR Deltacya double mutants restored rugose colonial morphology. Lowering intracellular cAMP levels in a DeltahapR mutant by the addition of glucose diminished VpsR expression and colonial rugosity. On the basis of our results, we propose a model for the regulatory input of CRP on exopolysaccharide biosynthesis.
Liang
Weili
W
Department of Microbiology, Biochemistry and Immunology, Morehouse School of Medicine, 720 Westview Dr. SW, Atlanta, GA 30310-1495, USA.
Silva
Anisia J
AJ
Benitez
Jorge A
JA
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018441:Biofilms; D000242:Cyclic AMP / Q000378:metabolism; D002373:Cyclic AMP Receptor Protein / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D009154:Mutation; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D053038:Quorum Sensing; D014734:Vibrio cholerae / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D011135:Polysaccharides, Bacterial; D000242:Cyclic AMP