Functional analysis of a Campylobacter jejuni nutrient transport protein using proteomics and metabolomics
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, Australia.
- Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia.
- Discipline of Pathology, School of Medical Sciences, The University of Sydney, Sydney, NSW, Australia.
Campylobacter jejuni is the leading cause of bacterial gastroenteritis in the developed world. Infection occurs predominantly through the consumption of undercooked/poorly prepared commercial chicken products. Importantly, C. jejuni exists mainly as a commensal organism within the intestines of chickens, but is pathogenic in humans. While the exact mechanism of this difference in pathogenicity is unknown, factors such as motility and nutrient uptake are thought to be significant. C. jejuni is generally considered assaccharolytic and primarily utilizes amino and organic acids as carbon sources. We conducted proteomic analysis of C. jejuni to identify proteins associated with growth in deoxycholate, mimicking gut bile salts encountered during human infection. We quantified 1561 proteins, and the most significantly induced protein was the product of the cj0025 gene, which has been previously annotated as a ’putative C4-dicarboxylate transport protein’. To determine the function of Cj0025, metabolomic profiles of media inoculated with C. jejuni wild-type or a Δcj0025 deletion strain were compared. Our results showed that the mutant was not impaired in the uptake of amino acids or organic acids, but was for cystine, a cysteine dimer. This was reflected both in the mutant proteome, which showed a downregulation of sulfur-related proteins, and a growth-inhibition assay utilising a toxic analogue of cystine.