Hydrogen-stimulated carbon acquisition and conservation in Salmonella enterica serovar Typhimurium

Salmonella enterica serovar Typhimurium can utilize molecular hydrogen for growth and amino acid transport during anaerobic growth. Via microarray we identified H(2) gas-affected gene expression changes in Salmonella. The addition of H(2) caused altered expression of 597 genes, of which 176 genes were upregulated and 421 were downregulated. The significantly H(2)-upregulated genes include those that encode proteins involved in the transport of iron, manganese, amino acids, nucleosides, and sugars. Genes encoding isocitrate lyase (aceA) and malate synthase (aceB), both involved in the carbon conserving glyoxylate pathway, and genes encoding the enzymes of the d-glucarate and d-glycerate pathways (gudT, gudD, garR, garL, garK) are significantly upregulated by H(2). Cells grown with H(2) showed markedly increased AceA enzyme activity compared to cells without H(2). Mutant strains with deletion of either aceA or aceB had reduced H(2)-dependent growth rates. Genes encoding the glutamine-specific transporters (glnH, glnP, glnQ) were upregulated by H(2), and cells grown with H(2) showed increased [(14)C]glutamine uptake. Similarly, the mannose uptake system genes (manX, manY) were upregulated by H(2,) and cells grown with H(2) showed about 2.0-fold-increased [(14)C]d-mannose uptake compared to the cells grown without H(2). Hydrogen stimulates the expression of genes involved in nutrient and carbon acquisition and carbon-conserving pathways, linking carbon and energy metabolism to sustain H(2)-dependent growth.