Mechanisms of Yersinia Enterocolitica Interaction with the Gut Microbiota - PROJECT SUMMARY/ABSTRACT The gut microbiota antagonizes infection with enteric pathogens in a process termed colonization resistance. Short chain fatty acids are considered a key component of colonization resistance, however, despite decades of research, the mechanism(s) of how short chain fatty acids exert colonization resistance and impede pathogen growth are incompletely understood. One of the main challenges in defining the mechanisms of short chain fatty acid toxicity has been that many gut bacteria, including enteric pathogens are inherently resistant. Disentangling mechanisms of toxicity and resistance has proven to be a major challenge. We discovered that Yersinia enterocolitica, a common cause of foodborne illness, is exquisitely sensitive to propionate under specific in vitro conditions, while fully resistant in other conditions. We posit that this this curious observation poses a unique opportunity to discover mechanisms of short chain fatty acid toxicity, as well as mechanisms of resistance. Based on our preliminary studies, we propose that propionate is erroneously converted by acetate kinase (AckA) and phosphate acetyltransferase (Pta) to propionyl-CoA, thus ensnaring the CoA pool and impeding acetyl-CoA metabolism. We will test key aspects of our hypothesis in vitro and in mouse models of infection using a strategic combination of bacterial and host genetics, metabolomics, and transcriptomics. We will pursue the following specific aims: 1. Determine the mechanism of propionate- mediated toxicity, and 2. Investigate the molecular mechanism(s) underlying Y. enterocolitica resistance to propionate in vitro and in vivo. Successful completion of this work is expected to reveal a novel molecular mechanism of short chain fatty acid-mediated toxicity; since Pta and AckA are widespread in bacteria, this mechanism may be applicable to gut bacteria in general. As such, these studies will advance our mechanistic understanding of how colonization resistance is achieved by the gut microbiota, and how enteric pathogens such as Y. enterocolitica can overcome colonization resistance.
