Studies of the microaerophilic nature of Campylobacter fetus subsp. jejuni. I. Physiological aspects of enhanced aerotolerance

Abstract

The aerotolerance of the microaerophilic bacterium Campylobacter fetus subsp. jejuni strain H840 (ATCC 29428) can be enhanced by addition of a combination of ferrous sulfate, sodium bisulfite, and sodium pyruvate (FBP), or of dihydroxyphenyl compounds such as nor-epinephrine (NE), to Brucella broth. Transport of ⁵⁵Fe³⁺ was increased by NE, suggesting that ordinary rates of transport, while adequate for growth at 6% O₂, might not permit growth at 21% O₂. Growth with FBP at 21% O₂ did not appreciably affect levels of cytochromes or of various tricarboxylic acid cycle enzyme activities. Activities of certain iron-dependent enzymes (succinate dehydrogenase and aconitate hydratase), and also respiration rates of whole cells, were lower in cells grown at 21% O₂ in Brucella broth compared to 6% O₂, but FBP did not cause an increase in these activities or rates. FBP caused a decrease in catalase and peroxidase activities. Total superoxide dismutase (SOD) activity increased when cells were grown at 21% O₂ with FBP. When grown without FBP, however, the organism possessed SOD activity as high as that in Escherichia coli, and a variant strain of H840 possessed nearly double this activity but was no more aerotolerant than the parent strain. A very oxygen-sensitive strain of C. fetus subsp. intestinalis also possessed high SOD activity. Consequently, total SOD activity in C. fetus does not appear to account for lack of aerotolerance. No evidence that FBPcauses any physiological change in C. fetus that could satisfactorily account for enhancement of aerotolerance could be obtained. It is possible that FBP or NE might not affect some physiological process in the organisms but might instead act on the culture medium.