Defining the role of YeiH in Salmonella pathogenesis

PROJECT SUMMARY Non-typhoidal Salmonella enterica (NTS) is a leading cause of bacterial foodborne gastroenteritis and leading cause of death amongst foodborne pathogens. NTS elicit neutrophilic inflammation both during gut colonization and in systemic infection. Neutrophils produce toxic products to kill invading pathogens. One toxic product produced by activated neutrophils during severe bacterial infection is sulfite. Sulfites are reactive sulfur species that are toxic to all life forms. In addition to their presence during severe bacterial infection, sulfites are endogenously produced during metabolism of sulfated amino acids and are ingested in food products. Sulfites are also added to food products as antimicrobial agents. Therefore, enteric pathogens such as NTS must resist sulfite toxicity in several stages of infection. Our preliminary data link yeiH with sulfite stress resistance in Salmonella Typhimurium. We show a ∆yeiH mutant is defective for growth in sulfite stress conditions and yeiH expression is specifically activated by sulfite. yeiH encodes a highly conserved putative inner membrane protein with no documented function. The purpose of the proposed work is to establish the role of YeiH in sulfite stress resistance. We hypothesize that YeiH exports sulfites to allow Salmonella to resist neutrophil-derived sulfite stress during infection. We will test our hypothesis in two aims. In Aim 1, we will establish the role of yeiH in infection. We will use animal models of colitis and sepsis to establish whether yeiH is needed for Salmonella fitness during infection. Using a yeiH transcriptional reporter as a novel sulfite biosensor, we will determine the tissues in which yeiH is expressed to establish the spatial organization of sulfite stress during enteric and systemic salmonellosis. In Aim 2, we will determine how YeiH contributes to sulfite stress resistance. We will determine whether the proton motive force drives YeiH function and establish the amino acid residues important for YeiH role in sulfite stress resistance. We will also establish whether YeiH function is to export sulfite from the cell. YeiH orthologs are present in many bacteria, including in different pathogens with importance to human health. Successful completion of the proposed experiments will allow us to establish how YeiH contributes to Salmonella sulfite stress resistance in vitro and in vivo. This work will lead to future studies to define the mechanism of YeiH function and establish how sulfites contribute to human health and resistance to bacterial infections.