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.
