Monster Seminar Jam - Pathogenic Vibrios in Shellfish
Dr. Anita Wright, Aquatic Food Production Laboratory, University of Florida
Vibrio species are indigenous to marine and estuarine environments. Although these bacteria are typically associated with human infectious diseases, such as cholera, their relationships with marine invertebrates and fish may have greater relevance to their survival and evolution. We are using PCR-based quantitative analysis (real-time PCR) and DNA fingerprinting (rep-PCR) in order to examine the environmental distribution of virulent V. vulnificus in the Gulf of Mexico. This species is a pathogen of both humans and fish, and our studies indicate that it may preferentially colonize Eastern oysters (Crassostrea virginica), compared to other shellfish. We are investigating the relevance of virulence factors, such as capsular polysaccharide (CPS) expression, to the ecology and environmental survival of V. vulnifiucs. Vertebrate animal models demonstrated that CPS expression correlates with virulence and opaque (O) colony morphology, but virulent phenotypes show phase variation to translucent (T) colony types with reduced CPS and virulence. We identified repetitive DNA elements in the CPS operon that are associated with deletion mutations that eliminate phase variation and capsule expression. Switching from O to T phenotype was induced under specific growth conditions, and rates were dependent on strain, media, and temperature, and increased with extended incubation. The transition to translucent phase promoted V. vulnificus attachment to surfaces and biofilm formation (Joseph and Wright, 2004). Therefore, these genetic variations may represent adaptations for increased survival in estuarine enviromnents.
Date and Time:
February 24, 2005,
11:00 am - 12:30 pm