EPIDEMIOLOGY, ECOLOGY, AND MOLECULAR GENETICS OF ANTIMICROBIAL RESISTANCE IN PATHOGENIC AND COMMENSAL BACTERIA FROM FOOD ANIMALS
Location: Bacterial Epidemiology and Antimicrobial Resistance
Title: Hydrogen-Stimulated Gene Expression by Salmonella enterica serovar Typhimurium in a Carbon Limited Environment
Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: May 21, 2011
Publication Date: May 21, 2011
Citation: Lamichlane-Khadka, R., Frye, J.G., Maier, R.J. 2011. Hydrogen-Stimulated Gene Expression by Salmonella enterica serovar Typhimurium in a Carbon Limited Environment. 111th General Meeting of the American Society for Microbiology. May 21-24,2011. New Orleans,LA. CDROM.
Background: Salmonella enterica serovar Typhimurium can utilize molecular hydrogen for growth and amino acid transport during anaerobic growth in a carbon limited environment. In this study we identified hydrogen-stimulated gene expression changes contributing to Salmonella survival. Methods: Microarray slides consisting of 4,596 annotated S. typhimurium LT2 ORFs were utilized for gene expression profiling of S. typhimurium strain JSG210 grown anaerobically with versus without hydrogen in an amino acid containing medium with no added sugar. Microarrays were performed in triplicates with dye swap between replicates. Real-time PCR was utilized to further validate the differential gene expression shown by the microarrays. aceA and aceB single gene deletion mutants were constructed using the lambda Red system. Results: DNA microarrays revealed significant alteration of 938 genes following exposure to hydrogen, of which 176 were up-regulated and 762 were down-regulated. Real-time PCR of select microarray-identified differentially expressed genes correlated significantly with the microarray data. The significantly H2-up-regulated genes included those that encode proteins involved in the transport of: iron (fhuA, fhuF, sitA, sitB, sitC, yciE, yciF); amino acids (artI, artP, glnH, glnP, glnQ); purine, pyrimidine, and nucleosides (pnuC); and sugars (rbsB, mglB, ugpB, manY, nagE). In addition, genes encoding isocitrate lyase (aceA) and malate dehydrogenase (aceB), both involved in the glyoxylate pathway, and allantoinase (allB) and glycerate kinase (garK), also involved in glyoxylate metabolism, were significantly up-regulated in cells grown in the presence of hydrogen. aceA and aceB single deletion mutants showed significantly reduced growth compared to the wild type JSG210 when grown with hydrogen in an amino acid only containing medium. This indicates that the glyoxylate bypass is required for the hydrogen-enhanced anaerobic growth of Salmonella in carbon limited conditions. A number of genes encoding virulence-associated proteins were significantly down-regulated. Conclusion: Addition of hydrogen stimulates the expression of genes involved in nutrient and carbon transport and the glyoxylate pathway in Salmonella growing under carbon limitation.