Vibrio vulnificus is an opportunistic human and animal pathogen that is predominantly found in estuarine waters. In aquatic ecosystems, it colonizes filter-feeders, such as oysters, and has been found to form biofilms on the surface of various marine organisms, including plankton, algae, fish, eels, and crustaceans. The bacterium can spontaneously develop a rugose phenotype, which is associated with the production of polysaccharide(s) that impart a raised, wrinkled appearance to cells, copious biofilm formation, and increased stress resistance. Biofilm and rugose colony development, along with pellicle and aggregate formation, are believed to be crucial for the environmental survival and persistence of V. vulnificus. As the biosynthesis of polysaccharide(s) is a key feature linking these physiological processes, the main objectives of this study were to identify polysaccharide loci contributing to survival phenotypes in V. vulnificus and to gain insight into the regulation of these loci. Two polysaccharide loci (brp and rbd) were found to contribute to biofilm formation. The brp locus is regulated by the second messenger c-di-GMP and by at least two transcriptional regulators BrpR and BrpT. Lesions in glycosyltransferases in the locus or in either of the regulators abated the inducing effects of c-di-GMP on biofilm formation. The rbd locus is regulated not by c-di-GMP, but instead by a response regulator (RbdG) belonging to the TCRS family, which is encoded within the locus. The biofilms associated with the expression of the brp and rbd polysaccharides were structurally unique and simultaneous expression of both loci dramatically enhanced pellicle formation. Each locus also provides unique survival characteristics; the development of rugosity and stress resistance could be attributed to brp expression whereas rbd expression augmented aggregate formation. The ability of V. vulnificus to differentially regulate expression of the brp and rbd polysaccharides may allow the bacterium to “fine tune” its biofilm lifestyle to maximally benefit from the characteristics associated with each locus.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/31773 |
| Date | 09 January 2012 |
| Creators | Guo, Yunzhi |
| Contributors | Rowe-Magnus, Dean |
| Source Sets | University of Toronto |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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