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<OL> <LI> Determine the importance of Salmonella genes specifically expressed in the lumen of the pig intestine to bacterial carriage and shedding. In this way, we will identify the bacterial determinants likely to be required for survival and growth. <LI> Investigate the global regulation of Salmonella genes by formate, an important signaling molecule of the ileum, the site of Salmonella colonization.
NON-TECHNICAL SUMMARY: Salmonellosis remains the leading cause of death in this country among foodborne diseases. Little is known about the mechanisms by which Salmonella is maintained in food-animal species that fail to show overt disease, including pigs. We plan to identify the genetic determinants of the bacteria and environmental cues of the intestinal tract that allow Salmonella survive and be carried by pigs. <P>APPROACH: 1.) We will identify Salmonella genes specifically expressed within the pig as a means to find those required for survival in the animal. We will use an in vivo gene expression selection to identify these genes, then test them for their importance in infection by making mutations of the genes and testing the resulting mutant strains for survival and carriage in pigs. 2.) We will use genomic expression analysis to identify changes in gene expression due to the presence of formate. DNA microarrays will be used to identify changes in Salmonella gene transcription in response to formate, a short chain fatty acid in abundance in the ileum, the site of Salmonella colonization and invasion.