Oxygen requirement and tolerance of Campylobacter jejuni

The pathogen Campylobacter jejuni is considered a microaerophile yet has been shown to grow in vitro in atmospheres with partial oxygen tension of 21%. To achieve a better understanding of its microaerophily, the oxygen requirement and tolerance of four C. jejuni strains were investigated by measuring their growth under different conditions, by performing bioinformatic analyses and by determining their metronidazole resistance. At high cell densities, C. jejuni showed similar growth under microaerobic and fully aerobic oxygen tensions, but did not grow under oxygen-depleted conditions. At low cell densities, the bacteria grew only under microaerobic conditions. Eighteen genes were identified bioinformatically as potential contributors to the differences in oxygen tolerance between strains. Among them, cj0203, cj0264c, cj0415, cj0425, cj0628, cj0629 and cj0864 were considered the top potential contributors. The oxygen tolerance of the four C. jejuni strains was different, and this tolerance positively correlated with their resistance to metronidazole. This study provided evidence that C. jejuni was an obligate microaerophile. The data indicated that the strains had different oxygen tolerances; it suggested that they could result in phenotypic and physiological differences between strains grown under the same conditions. These differences could modulate the outcome of experiments, and may explain discrepancies in the results between strains.