UBC Theses and Dissertations
Campylobacter jejuni metabolism in survival and host cell interactions Pryjma, Mark Christopher
Campylobacter jejuni is a leading cause of foodborne bacterial gastroenteritis in both developed and developing nations. Although C. jejuni is a common environmentally acquired pathogen, it is quite fastidious, rapidly losing viability in aerobic conditions. Genome sequence analyses have failed to identify classical virulence factors, making the pathogenic success of C. jejuni a mystery. Mutational analysis described herein identified novel metabolic factors that are important for infection of human epithelial cells as well as generation of oxidative stress in C. jejuni during aerobic incubation. Investigation of a novel operon, fdhTU, induced during C. jejuni epithelial infection, showed that FdhTU positively regulates formate dehydrogenase. Subsequent analyses found that fdhTU and formate dehydrogenase are important for recovery of C. jejuni from epithelial cells. Further work showed that intracellular C. jejuni are undergoing oxidative stress, and that neutralization of oxidative stress with sulfite or catalase could significantly enhance recovery of C. jejuni following epithelial cell infection. Analyses of other respiratory dehydrogenases failed to identify other systems important for recovery of C. jejuni from epithelial cells, but did identify a role for gluconate dehydrogenase in reducing necrosis in T84 epithelial cells in a reactive oxygen species- and calpain-dependent manner. In addition to the importance for epithelial cell infection, metabolic features were also found to be involved in causing oxidative stress in C. jejuni under aerobic conditions. C. jejuni was found to produce H₂O₂ when incubated in aerobic but not microaerobic conditions at 37ºC but not 4ºC, with formate dehydrogenase and sulfite oxidoreductase dependent respiration important for H₂O₂ production. Sulfite and cysteine could reduce C. jejuni loss of viability in aerobic conditions in a manner dependent on the sulfur assimilation pathway protein Atps. Atps was identified as important for aerobic survival, H₂O₂ resistance, and in reducing H₂O₂ produced by formate dehydrogenase dependent respiration. Characterization of the role of multiple respiratory systems in C. jejuni, a bacterial model that shares little with other common pathogenic bacteria, has identified a central role of respiration in epithelial cell infection and environmental survival.
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