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Journal of Bacteriology, January 2009, p. 169-177, Vol. 191, No. 1
0021-9193/09/$08.00+0     doi:10.1128/JB.01307-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Distinct Sensory Pathways in Vibrio cholerae El Tor and Classical Biotypes Modulate Cyclic Dimeric GMP Levels To Control Biofilm Formation{triangledown} ,{dagger}

Brian K. Hammer1,{ddagger} and Bonnie L. Bassler1,2*

Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544-1014,1 Howard Hughes Medical Institute, Chevy Chase, Maryland2

Received 16 September 2008/ Accepted 17 October 2008

Quorum sensing (QS), or cell-cell communication in bacteria, is achieved through the production and subsequent response to the accumulation of extracellular signal molecules called autoinducers (AIs). To identify AI-regulated target genes in Vibrio cholerae El Tor (V. choleraeEl), the strain responsible for the current cholera pandemic, luciferase expression was assayed in an AI– strain carrying a random lux transcriptional reporter library in the presence and absence of exogenously added AIs. Twenty-three genes were identified and shown to require the QS transcription factor, HapR, for their regulation. Several of the QS-dependent target genes, annotated as encoding hypothetical proteins, in fact encode HD-GYP proteins, phosphodiesterases that degrade the intracellular second messenger cyclic dimeric GMP (c-di-GMP), which is important for controlling biofilm formation. Indeed, overexpression of a representative QS-activated HD-GYP protein in V. choleraeEl reduced the intracellular concentration of c-di-GMP, which in turn decreased exopolysaccharide production and biofilm formation. The V. cholerae classical biotype (V. choleraeCl), which caused previous cholera pandemics and is HapR–, controls c-di-GMP levels and biofilm formation by the VieA signaling pathway. We show that the VieA pathway is dispensable for biofilm formation in V. choleraeEl but that restoring HapR in V. choleraeCl reestablishes QS-dependent repression of exopolysaccharide production. Thus, different pandemic strains of V. cholerae modulate c-di-GMP levels and control biofilm formation in response to distinct sensory pathways.

* Corresponding author. Mailing address: Howard Hughes Medical Institute, Department of Molecular Biology, Princeton University, Princeton, NJ 08544-1014. Phone: (609) 258-2857. Fax: (609) 258-2957. E-mail: bbassler{at}princeton.edu

{triangledown} Published ahead of print on 24 October 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

{ddagger} Present address: School of Biology, Georgia Institute of Technology, Atlanta, GA 30332-0230.

Journal of Bacteriology, January 2009, p. 169-177, Vol. 191, No. 1
0021-9193/09/$08.00+0     doi:10.1128/JB.01307-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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