Molecular Analysis of Bacterial Adaptive Response to Host Reactive Species

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Infectious diarrhea afflicts a billion people a year and is responsible for approximately 4% of all human deaths worldwide. Salmonella enterica are common causes of infectious diarrhea in humans, and often plague active military servicemen and veterans. Salmonella are among the most frequent bacterial isolates resistant to antibiotics. The antibiotic resistance crisis is becoming a clinical problem of epic proportions, as the number of therapeutic compounds in the pipeline is dwindling. Future prophylactic and therapeutic approaches against drug resistant bacteria will greatly benefit from the identification of molecular targets in pathogens. During the last 20 years only 4 novel compounds have been introduced in the clinic, all of which represent new mechanisms identified through basic understanding of molecular pathogenesis. As holds true for all human pathogens, precise regulation of RNA polymerase controls essential aspects of Salmonella pathogenesis, and the expression of antibiotic resistant programs. Our investigations have shown that allosteric interactions of DksA and Gre factors with RNA polymerase regulate vital facets of Salmonella pathogenesis and antibiotic resistance. The proposed research will elucidate the mechanisms by which the DnaK/DnaJ chaperone couple regulates interactions of DksA with RNA polymerase, thereby engaging fundamental Salmonella virulence programs. We will also characterize how binding of Gre factors to the secondary channel of RNA polymerase provides a previously unsuspected level of regulation of Salmonella pathogenesis and antibiotic tolerance. Specifically, we will test the role that the transcriptional proofreading associated with Gre factors plays in resistance of Salmonella to the bactericidal activity inherent to the NADPH oxidase. Our investigations will also characterize how Gre factors modulate the expression of a type III secretion system that is vital to the intracellular lifestyle of Salmonella, while bolstering resistance to aminoglycoside antibiotics that poison bacterial translation. Our investigations will aid in the rational development of future therapies against a variety of Gram-negative, antibiotic resistant bacteria that cause high rates of morbidity and mortality in active servicemen, veterans and their families.