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Applied and Environmental Microbiology, July 2008, p. 4199-4209, Vol. 74, No. 13
0099-2240/08/$08.00+0 doi:10.1128/AEM.00176-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Caroline Wilde,2,
and
Dean A. Rowe-Magnus1,2*
Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada M5G 1L5,1 Division of Clinical Integrative Biology, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, S1-26A, Toronto, Ontario, Canada M4N 3N52
Received 18 January 2008/ Accepted 6 May 2008
Vibrio vulnificus is a human and animal pathogen that carries the highest death rate of any food-borne disease agent. It colonizes shellfish and forms biofilms on the surfaces of plankton, algae, fish, and eels. Greater understanding of biofilm formation by the organism could provide insight into approaches to decrease its load in filter feeders and on biotic surfaces and control the occurrence of invasive disease. The capsular polysaccharide (CPS), although essential for virulence, is not required for biofilm formation under the conditions used here. In other bacteria, increased biofilm formation often correlates with increased exopolysaccharide (EPS) production. We exploited the translucent phenotype of acapsular mutants to screen a V. vulnificus genomic library and identify genes that imparted an opaque phenotype to both CPS biosynthesis and transport mutants. One of these encoded a diguanylate cyclase (DGC), an enzyme that synthesizes bis-(3'-5')-cyclic-di-GMP (c-di-GMP). This prompted us to use this DGC, DcpA, to examine the effect of elevated c-di-GMP levels on several developmental pathways in V. vulnificus. Increased c-di-GMP levels induced the production of an EPS that was distinct from the CPS and dramatically enhanced biofilm formation and rugosity in a CPS-independent manner. However, the EPS could not compensate for the loss of CPS production that is required for virulence. In contrast to V. cholerae, motility and virulence appeared unaffected by elevated levels of c-di-GMP.
Published ahead of print on 16 May 2008.
These authors contributed equally to this work.
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