A fundamental question in cell biology is how metabolic pathways are integrated and controlled to produce a balanced, efficient metabolism. In addressing this question, the long term goal of research in the Downs lab is to gain a molecular understanding of regulatory and metabolic interactions amongst pathways. A solid understanding of such metabolic integration underlies efforts to predict the response of cells to environmental change, efforts to develop metabolic modeling systems, and efforts targeting metabolism for rational drug design and/or production of small molecules. We use Salmonella enterica for these studies because of the well-characterized genetic system and advanced understanding of biosynthetic pathways in this organism. Without a genetic system, engineering the mutant strains needed to address complex metabolic questions would hamper our progress. Our model system is centered around the biosynthesis of thiamine, with a particular focus on the synthesis of the pyrimidine moiety (HMP) of thiamine pyrophosphate (TPP) independent of the first step in de novo purine biosynthesis. The biosynthesis of an essential vitamin has proven to be an attractive model system for examining interactions between metabolic pathways. Work in the lab has been instrumental in demonstrating that interrupting many distinct metabolic pathways can have effects on thiamine synthesis. Thus far this work has idenitifed a number of uncharacterized ORFs and led into a variety of metabolic processes, including, but not limited to; carbon catabolism, Fe-S cluster metabolism, mutageneis, branched chain amino acid biosynthesis, tryptophan biosynthesis and CoA metabolism. In attempting to understand the puzzle of metabolism, we employ a variety of classical and modern techniques, both biochemical and genetic.

• Microbiology 303: Biology of Microorganisms

• Editor in Chief, Microbiology and Molecular Biology Reviews
• Trainer, NIH Genetics Training Program
• Trainer, Biotechnology Graduate Training Program