Location: Produce Safety and Microbiology ResearchTitle: Biological roles of the O-methyl phosphoramidate capsule modification in Campylobacter jejuni Author
|Van Alphen, Lieke|
|Miller, William - Bill|
Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2014
Publication Date: 1/30/2014
Citation: Van Alpen, L., Wenzel, C.Q., Richards, M., Fodor, C., Ashmus, R.A., Stahl, M., Karlyshev, A.V., Wren, B.W., Stintzi, A., Miller, W.G., Lowrey, T.L., Szymanski, C.M. 2014. Biological roles of the O-methyl phosphoramidate capsule modification in Campylobacter jejuni. PLoS One. 9(1):e87051. Interpretive Summary: Campylobacter strains decorate their outer surface in part through the addition of sugar molecules or other molecules. One such molecule is phosphoramidate. Phosphoramidate was identified on multiple campylobacters and helicobacters and is much more prevalent within this group of bacteria. Phosphoramidate groups have also been found on the outer surface of other bacterial pathogens. A mutant unable to transfer phosphoramidiate to the outer surface demonstrated an increased invasion of human cells, but a decreased resistance to anti-bacterial molecules present in human blood serum. The phosphoramidate mutant colonized chickens to levels similar to that of typical campylobacters; however, colonization of piglets was reduced 5-fold. Additionally, no difference was observed in a waxmoth larvae model. Waxmoth larvae were not killed by direct injection of the sugar molecules, indicating that the sugar molecules were not insecticidal.
Technical Abstract: Campylobacter jejuni is a major cause of bacterial gastroenteritis worldwide, and the capsular polysaccharide (CPS) of this organism is required for persistence and disease. C. jejuni produces over 47 different capsular structures, including a unique O-methyl phosphoramidate (MeOPN) modification present in at least 70% of all C. jejuni strains. Although the MeOPN structure is rare in nature it has structural similarity to synthetic pesticides. In this study, we have demonstrated by whole genome comparisons and high resolution magic angle spinning NMR that MeOPN modifications are common to most members of the Campylobacteraceae. These phospho-linked modifications are similar to phosphocholine modifications found on the surface polysaccharides of mucosal pathogens such as Haemophilus, Neisseria, and Streptococcus species, which have been shown to influence both invasion and serum resistance. Using a MeOPN transferase mutant generated in C. jejuni strain 81-176, we observed that loss of MeOPN from the cell surface correlated with increased invasion of Caco-2 epithelial cells and reduced resistance to killing by human serum, which were opposite to the affects observed with phosphocholine in the other mucosal pathogens. The C. jejuni mutant showed similar levels of colonization relative to the wild-type in the chicken commensal model, but showed a five-fold drop in colonization when co-infected with the wild-type in the piglet pathogenesis model. In Galleria mellonella waxmoth larvae, the MeOPN transferase mutant was able to kill the insects at wild-type levels. Furthermore, injection of the larvae with synthesized MeOPN, MeOPN-linked monosaccharides, or CPS purified from the wild-type strain did not result in larval killing, indicating that MeOPN does not have inherent insecticidal activity.