GENETIC & METABOLIC ADAPTATION BY SALMONELLA TO THE NATURAL ENVIRONMENT

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Salmonella is generally considered a low-frequency commensal and low-grade pathogen with very limited ability to survive long term in the environment outside of a host organism. Recent work has identified a constellation of interactive metabolic functions shared by all Salmonellae, but absent from its nearest relative E. coli. The constellation of Salmonella-specific functions includes de novo synthesis of cobalamin (B12), use of B12 in degradation of ethanolamine and propanediol, anaerobic respiration of tetrathionate to thiosulfate (ttr genes), and subsequent reduction to sulfite (phs genes) and sulfide (asr genes). All these functions would be used when Salmonella grows anaerobically on ethanolamine or propanediol in the presence of reducible sulfur compounds. Under these conditions, Salmonella forms granules of mineral sulfur, which it (but not E. coli) can later reduce by a process that requires the phs genes. While these functions may be important to pathogenesis, we think it more likely that they suggest a significant lifestyle for Salmonella in particular soil environments. Our work has been geared to understanding whether there is an environmental niche for Salmonella and the potential impact that such an ecological niche will have on our understanding of the pathogenesis of this organism.