Campylobacter jejuni is recognized as the most common pathogen responsible for bacterial gastroenteritis in the developed world, with the route of infection involving under-cooked or poorly prepared poultry as the organism resides as a commensal in the intestines of avian species. The ability of C. jejuni to survive in a diverse range of environments, colonise chickens and to adhere to and invade human gut epithelial cells has been strongly linked to factors including motility and the ability to uptake and utilise ‘unusual’ nutrients, especially organic and amino acids, rather than sugars. C. jejuni encodes a putative C₄-dicarboxylate transporter (gene designation cj0025c) that has been identified as the most up-regulated protein in proteomics analysis of C. jejuni grown under conditions of stress that mimic human hosts. The function of Cj0025c however, as well as the substrate it transports, remain unknown. Here, we use quantitative mass spectrometry-based proteomics using both iTRAQ and SWATH methods to compare proteomes of wild-type 11168H and cj0025c knockout strains with and without additional treatment conditions.

iTRAQ-based proteomic analysis of the Δcj0025c mutant revealed several functional clusters of proteins changing in abundance, including proteins involved in lipooligosaccharide modification and flagellar motility. SWATH-based proteomics successfully validated the Δcj0025c versus wild-type proteome comparison, and revealed clusters of proteins with altered abundance when cells were subjected to osmotic stress, including ribosomal and tryptophan biosynthesis proteins.