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Abstract
Previously considered asaccharolytic, it is now known that 65% of sequenced Campylobacter jejuni isolates possess the fuc operon encoding enzymes for L-fucose and D-arabinose catabolism. C. jejuni 11168, a fuc+ strain, outcompetes its fucose permease mutant in colonizing a piglet model for diarrheal disease. Transfer of the fuc locus into a fuc- strain (C. jejuni 81-176) enables 81-176 to metabolize and swim to L-fucose and D-arabinose, suggesting that a fuc product is responsible for coordinating carbohydrate detection and chemotaxis. Mutagenesis studies of the fuc genes suggest that a dehydrogenase coordinates this response, and that the protein alone is responsible for this phenotype since transfer of the single protein into 81-176 also confers chemotaxis. A model has been established for L-fucose and D-arabinose metabolism based on growth experiments of metabolic mutants, homology comparisons to known enzymes, and NMR studies to detect metabolic products.
There is also evidence that the microbiota plays a role in L-fucose foraging by helping C. jejuni obtain L-fucose and that sugar-metabolizing strains may possess a different repertoire of carbohydrate adhesins that impact C. jejuni colonization in the gastrointestinal tract during human infections. Fucosylated human milk oligosaccharides (HMOs) are generally considered protective against C. jejuni infections by serving as binding decoys; however, 16S sequencing of stool samples from children in low-to-middle-income countries (LMICs) revealed high Campylobacter burdens in breastfed infants. Yet there appears to be a selection against fuc+ strains, suggesting that HMOs are preferentially bound by fuc+ strains and thus act as decoys, but in turn allow fuc- strains to proliferate. RNAseq experiments were done to compare the transcriptomes of 11168 and 81-176 in the presence of human breastmilk. Additionally, binding studies with liquid glycan arrays reveal 11168 binds more oligosaccharides than 81-176 and we await sequencing results to determine the carbohydrate binding preferences of these strains. Future work will further elucidate the role of breastfeeding in C. jejuni infections by examining RNAseq data and verifying that differences in metabolic and binding activities identified in the two model laboratory strains extends to the laboratory collection of human isolates from LMICs.
There is also evidence that the microbiota plays a role in L-fucose foraging by helping C. jejuni obtain L-fucose and that sugar-metabolizing strains may possess a different repertoire of carbohydrate adhesins that impact C. jejuni colonization in the gastrointestinal tract during human infections. Fucosylated human milk oligosaccharides (HMOs) are generally considered protective against C. jejuni infections by serving as binding decoys; however, 16S sequencing of stool samples from children in low-to-middle-income countries (LMICs) revealed high Campylobacter burdens in breastfed infants. Yet there appears to be a selection against fuc+ strains, suggesting that HMOs are preferentially bound by fuc+ strains and thus act as decoys, but in turn allow fuc- strains to proliferate. RNAseq experiments were done to compare the transcriptomes of 11168 and 81-176 in the presence of human breastmilk. Additionally, binding studies with liquid glycan arrays reveal 11168 binds more oligosaccharides than 81-176 and we await sequencing results to determine the carbohydrate binding preferences of these strains. Future work will further elucidate the role of breastfeeding in C. jejuni infections by examining RNAseq data and verifying that differences in metabolic and binding activities identified in the two model laboratory strains extends to the laboratory collection of human isolates from LMICs.