The gastrointestinal pathogen Campylobacter jejuni metabolizes sugars with potential help from commensal Bacteroides valgatus

Authors: GARBER, JOLENE - University Of Georgia; NOTHAFT, HARALD - University Of Alberta; PLUVINAGE, BEN - University Of Victoria; STAHL, MARTIN - University Of Ottawa; BIAN, XIAOMING - University Of Georgia; PORFIRIO, SARA - University Of Georgia; ENRIQUEZ, AMBER - University Of Georgia; BUTCHER, JAMES - Carleton University - Canada; HUANG, HUA - University Of Illinois; GLUSHKA, JOHN - University Of Georgia; Line, John; GERLT, JOHN - University Of Illinois; AZADI, PARASTOO - University Of Georgia; STINTZI, ALAIN - University Of Ottawa; BORASTON, ALISDAIR - University Of Victoria; SZYMANSKI, CHRISTINE - University Of Georgia

Submitted to: Communications Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2019
Publication Date: 1/7/2020
Citation: Garber, J.M., Nothaft, H., Pluvinage, B., Stahl, M., Bian, X., Enriquez, A., Butcher, J., Huang, H., Glushka, J., Line, J.E., Gerlt, J.A., Azadi, P., Stintzi, A., Boraston, A.B., Szymanski, C.M., Porfirio, S. 2020. The gastrointestinal pathogen Campylobacter jejuni metabolizes sugars with potential help from commensal Bacteroides valgatus. Communications Biology. 3(1):2. https://doi.org/10.1038/s42003-019-0727-5.
DOI: https://doi.org/10.1038/s42003-019-0727-5

Interpretive Summary: Campylobacter jejuni is a common commensal in chickens and often transmitted to humans through consumption of undercooked or contaminated food products where it causes gastrointestinal infections. C. jejuni was once considered asaccharolytic (unable to utilize sugars) since it lacks key enzymes for carbohydrate metabolism. Greater than half of sequenced Campylobacter jejuni isolates possess a pathway for L-fucose utilization. We identified a functional locus for L-fucose utilization (cj0480c-cj0489 in C. jejuni NCTC 11168) that exists in approximately 65% of sequenced strains. This work describes the characterization of Cj0485 through crystallography, enzymology and multiple biological assays to confirm its function as a fucose dehydrogenase, which we subsequently named FabG. This led to the discovery that FabG is also capable of reducing arabinose and is the sole component encoded by the fuc operon necessary for chemotaxis to both sugars. NMR and mutagenesis studies provided further insight into the mechanism of L-fucose breakdown and allowed us to propose a pathway for L-fucose and D-arabinose catabolism. By better understanding the role of carbohydrate metabolism in C. jejuni and how the other carbon sources and microbial species in the gut can influence this interaction, we may be able to better understand how nutrition influences Campylobacter carriage and disease severity.

Technical Abstract: Fucosylated structures are abundant on epithelial cell surfaces, intestinal mucosa, plant digests and human milk oligosaccharides. Greater than half of sequenced Campylobacter jejuni isolates possess a pathway for L-fucose utilization. In C. jejuni NCTC11168, this operon is necessary for L-fucose chemotaxis and competitive colonization in a piglet diarrheal disease model, but the steps involved in L-fucose catabolism remain unknown. In this work, the structure of a putative dehydrogenase necessary for chemotaxis, Cj0485, was solved in complex with NADP and resembles FabG, the L-fucose dehydrogenase of Burkholderia multivorans. The C. jejuni FabG reduces both L-fucose and D-arabinose in vitro and both sugars are catabolized by the enzymes encoded by the fuc operon. NMR studies with 13C-L-fucose identified the intermediates leading to the production of pyruvate and lactate. This also allowed us to propose a pathway for L-fucose and D-arabinose catabolism. Although C. jejuni lacks glycosidases for sugar release, the organism exhibits enhanced growth when co-incubated with the gut microbe, Bacteroides vulgatus, both in vitro and in vivo. Yet when excess amino acids are available, C. jejuni shows a preference for their use providing evidence that a metabolic hierarchy exists linking through the TCA cycle. Overall, this work increases our understanding of nutrient metabolism by this common foodborne pathogen and highlights a possible commensal relationship with other gut microbes.