UNRAVELING VIBRIO PARAHAEMOLYTICUS PATHOGENESIS BY USING A FUNCTIONAL GENOMICS APPROACH

Vibrio parahaemolyticus is a serious threat to the consumer of molluscan shellfish in the United States and has led to a significant number of illnesses and closures of shellfish harvesting areas over the past two summers. We will identify virulence mechanisms in V. parahaemolyticus in order to better understand the regulation of V. parahaemolyticus pathogenicity and to differentiate pathogenic strains from nonpathogenic strains. To date, two toxin-producing genes have been identified in V. parahaemolyticus; however, analyses have shown that strains lacking these toxins and genomic regions can still be pathogenic, indicating that important virulence factors remain to be identified. One of the key virulence genes in V. parahaemolyticus and V. cholerae is the toxRS gene which regulates at least one of the toxins produced in most pathogenic strains. We will determine the range of genes that are regulated by the toxRS gene in V. parahaemolyticus by examining a toxRS deletion mutant already developed by our collaborator, Dr. Fidelma Boyd. We will examine the transcriptome (the full complement of unique RNA molecules with coded transcripts) and proteome (the set of proteins specified by genes within an organism). We will perform expression analyses using a V. parahaemolyticus whole genome microarray to determine the range of genes up and down regulated in the toxRS mutant strain compared to the wild-type strain. The toxRS gene will also be evaluated as a possible regulator of a potential virulence enhancer identified by ARS research as phosphoglucose isomerase containing a lysyl aminopeptidase (PGI-LysAP) activity. The virulence of the toxRS mutant will be assayed by in vitro and in vivo invasion assays. Overall, we will identify potential virulence mechanisms associated with V. parahaemolyticus and will determine if PGI-LysAP transcription is regulated by the toxRS gene. New assay methods for pathogenic strains of V. parahaemolyticus, including the recently emerged O3:K6 pandemic strain of V. parahaemolyticus, will be developed with the ultimate goal of reducing outbreaks of illness among shellfish consumers and the impediments that such outbreaks have on the industry and other stakeholders.