Oxygen toxicity in Campylobacter jejuni: physiological comparison of a microaerophilic wild-type strain with an aerotolerant mutant
A comparative study of the microaerophilic Campylobacter jejuni strain H840 with an aerotolerant mutant, MC711-01, revealed that catalase and, to a lesser extent, SOD activity is correlated with the aerotolerance and enhanced resistance of MC7ll-0l to H₂O₂. When cells were cultured under 6% oxygen, the specific activity of catalase was significantly higher in crude extracts of MC711-01 than of H840. The catalase activity of MC711-01 more than doubled when cells were cultured under 21% oxygen, and this activity was 2.6 times greater than that of H84O; no corresponding increase was observed in strain H840. There was no significant difference in the mean SOD activity of the two strains when cultured under 6% oxygen or in H840 cells cultured under either 6% or 21% oxygen; however, the SOD activity of MC711-01 increased 1.5 times when cells were cultured under 21% oxygen.
Survival studies revealed that MC711-01 was significantly more E resistant to H₂O₂ when cultured under either 6% or 21% oxygen. However, both MC711-01 and H84O were more susceptible to H₂O₂ when grown under 21% oxygen, indicating that both strains might be more highly stressed when the cells are grown at this oxygen tension.
The present study suggests that in C. jejuni, the level of catalase activity may influence the degree of susceptibility to H₂O₂ and consequently, the degree of aerotolerance.