UBC Theses and Dissertations
Initial characterization of peptidoglycan O-acetylation and the effects on colonization factors of Campylobacter jejuni Ha, Reuben Danny
Campylobacter jejuni is a leading cause of bacterial gastroenteritis in the developed world. Despite its prevalence, its pathogenesis is poorly understood. It lacks clear virulence factors such as those described for other enteropathogens. The characteristic helical shape of C. jejuni, maintained by the peptidoglycan (PG) layer, is important for colonization and host-pathogen interactions. Therefore, changes in morphology and the underlying PG greatly affect the physiology and biology of the organism. O-Acetylation of Peptidoglycan (OAP) is a phenomenon by which bacteria acetylate the C6 hydroxyl group of N-acetylmuramic acid in the glycan backbone to confer resistance to lysozyme and control lytic transglycosylase activity. The OAP gene cluster consists of a transmembrane PG O-acetyltransferase A (patA) for translocation of acetate into the periplasm, a periplasmic PG O-acetyltransferase B (patB) responsible for O-acetylation of N-acetylmuramic acid (MurNAc), and an O-acetylpeptidoglycan esterase (ape1) for de-O-acetylation. Reduced OAP in ΔpatA and ΔpatB has a minimal effect on growth and fitness under the conditions tested. However, accumulation of OAP in Δape1 results in marked differences in peptidoglycan biochemistry including changes in O-acetylation levels, anhydromuropeptide levels, and PG changes not expected to be a direct result of Ape1 activity. This suggests that OAP may be a form of substrate level regulation in PG metabolism. Ape1 acetylesterase activity was confirmed in vitro using p-nitrophenyl acetate and O-acetylated PG as substrates. In addition, Δape1 exhibits defects in pathogenesis-associated phenotypes including cell shape, motility, biofilm formation, and sodium deoxycholate sensitivity. The mutant is also impaired for chick colonization and adhesion, and invasion and intracellular survival in INT407 epithelial cells lines in vitro. The importance of Ape1 activity to C. jejuni biology makes it a good candidate as a novel antimicrobial target.
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