Insights into the molecular basis of the microaerophily of three Campylobacterales: a comparative study

The concentration of oxygen in the atmosphere is a common environmental factor which can also be a source of stress for microorganisms. Comparative analyses of the responses of the epsilon-Proteobacteria Campylobacter jejuni, Helicobacter pylori and Wolinella succinogenes to elevated oxygen concentrations were carried out using transcriptomics. Microarray data were analysed to determine genes differentially expressed under elevated oxygen concentrations. The results indicated 158, 58 and 82 genes were upregulated and 46, 40 and 65 were downregulated in C. jejuni, H. pylori and W. succinogenes, respectively. The gene encoding the enzyme alkyl hydroperoxide reductase was the only one upregulated at higher oxygen tensions in all three bacterial species. No genes were found to be downregulated in all three species. Functional classification analyses were performed on the genes whose expression was modulated in order to identify common pathways and functional categories which were differentially expressed in the three organisms. Processes upregulated at higher oxygen tensions included translation, oxidative phosphorylation, antioxidation, and nucleic acid metabolism. ABC and ion-coupled transport proteins were generally downregulated at higher oxygen tensions. Finally, insights into the preferred environment were gained from the analyses of the bacterial responses, specifically motility and chemotaxis proteins. W. succinogenes preferred anaerobic conditions as opposed to C. jejuni and H. pylori preference for microaerobic conditions. These comparative studies provide a better understanding of bacterial adaptation to and interaction with their environment.