The steady flow of metabolites through the living cell is accomplished by a complex interaction between many metabolic pathways. These interactions must be closely regulated to guarantee balanced growth of the cell. Regulation occurs on a variety of levels including gene expression, feedback inhibition and regulation of both metabolite pool sizes and their ratios. This regulation reflects the environmental stimuli affecting the cell. One such stimulus that is particularly relevant to this work is the amount of molecular oxygen available. I have uncovered a novel, anaerobically induced pathway for synthesis of the pryimidine moiety of thiamine (vitamin B1) in Salmonella typhimurium. This pathway is designated alternative pyrimidine biosynthesis or apb. The apb pathway appears to be required for synthesis of the pyrimidine moiety of thaimine in wild-type cells during anaerobic growth in medium containing high levels of purines. It is plausible that these growth conditions reflect those found by S. typhimurium in its natural habitat of the gut. Vitamin B1 is an essential vitamin required for both biosynthesis and energy generation. The biosynthesis of this vitamin has been studied in the past, however, many aspects of this pathway remain unexplored. S. typhimurium is a facultative anaerobe with a well established genetic system that we can use to explore the apb pathway which is clearly physiologically relevant to the anaerobic lifestyle of Salmonella typhimurium. We are interested not only in the apb pathway per se but also in the interactions it may have with other metabolic pathways both aerobically and anaerobically. A comprehensive study on the biochemical and genetic components of the apb pathway will be initiated. For this purpose modern chemical, biochemical, molecular biological and genetic techniques will be employed. This encompassing approach will allow us to gain insight in a number of areas related to this problem, such as: the metabolic origin of the atoms in the pyrimidine synthesized through the apb pathway, the number of gene products involves, the regulation of gene expression of this pathway at different levels and in the long run, to unravel the interactions between this and other pathways. We believe that the investigation of this pathway will contribute to our understanding of the global metabolic strategies that S. typhimurium uses to survive in its natural anaerobic environment by utilizing redundant pathways which are regulated differentially. In addition these studies will further our knowledge of genes whose expression is regulated by oxygen.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM047296-03
Application #
2184714
Study Section
Microbial Physiology and Genetics Subcommittee 2 (MBC)
Project Start
1993-01-01
Project End
1996-12-31
Budget Start
1995-01-01
Budget End
1995-12-31
Support Year
3
Fiscal Year
1995
Total Cost
Indirect Cost
Name
University of Wisconsin Madison
Department
Microbiology/Immun/Virology
Type
Schools of Earth Sciences/Natur
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
Ernst, Dustin C; Downs, Diana M (2015) The STM4195 gene product (PanS) transports coenzyme A precursors in Salmonella enterica. J Bacteriol 197:1368-77
Palmer, Lauren D; Paxhia, Michael D; Downs, Diana M (2015) Induction of the Sugar-Phosphate Stress Response Allows Saccharomyces cerevisiae 2-Methyl-4-Amino-5-Hydroxymethylpyrimidine Phosphate Synthase To Function in Salmonella enterica. J Bacteriol 197:3554-62
Bazurto, Jannell V; Heitman, Nicholas J; Downs, Diana M (2015) Aminoimidazole Carboxamide Ribotide Exerts Opposing Effects on Thiamine Synthesis in Salmonella enterica. J Bacteriol 197:2821-30
Bazurto, Jannell V; Downs, Diana M (2014) Amino-4-imidazolecarboxamide ribotide directly inhibits coenzyme A biosynthesis in Salmonella enterica. J Bacteriol 196:772-9
Palmer, Lauren D; Leung, Man Him; Downs, Diana M (2014) The cysteine desulfhydrase CdsH is conditionally required for sulfur mobilization to the thiamine thiazole in Salmonella enterica. J Bacteriol 196:3964-70
Palmer, Lauren D; Downs, Diana M (2013) The thiamine biosynthetic enzyme ThiC catalyzes multiple turnovers and is inhibited by S-adenosylmethionine (AdoMet) metabolites. J Biol Chem 288:30693-9
Palmer, Lauren D; Dougherty, Michael J; Downs, Diana M (2012) Analysis of ThiC variants in the context of the metabolic network of Salmonella enterica. J Bacteriol 194:6088-95
Christopherson, Melissa R; Lambrecht, Jennifer A; Downs, Deanna et al. (2012) Suppressor analyses identify threonine as a modulator of ridA mutant phenotypes in Salmonella enterica. PLoS One 7:e43082
Boyd, Jeffrey M; Teoh, Wei Ping; Downs, Diana M (2012) Decreased transport restores growth of a Salmonella enterica apbC mutant on tricarballylate. J Bacteriol 194:576-83
Koenigsknecht, Mark J; Lambrecht, Jennifer A; Fenlon, Luke A et al. (2012) Perturbations in histidine biosynthesis uncover robustness in the metabolic network of Salmonella enterica. PLoS One 7:e48207

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