Full text loading...
Aerobic Growth of Campylobacter sputorum subspecies bubulus with Formate
Abstract
Formate stimulated growth of the microaerophilic bacterium Campylobacter sputorum subsp. bubulus at reduced dissolved oxygen tensions (d.o.t). At a d.o.t. of 2 kPa the mean doubling time of C. sputorum growing in a complex medium supplemented with formate was 2 h. Growth did not occur in the absence of O2. When C. sputorum was cultured in a complex medium with formate, growth and formate consumption slowed down after a rise of the d.o.t. from 2 to 15 kPa. At the same time the potential respiration rate diminished greatly. The effects of exposure to a d.o.t. of 15 kPa could still be reversed after 4 h by shifting the d.o.t. back to 2 kPa. The decrease in the potential respiration rate could be related to a loss of formate dehydrogenase activity. Its susceptibility to a high d.o.t. was greater when formate was present in the growth medium than in its absence. Formate oxidase had a low affinity for O2 and H2O2 was a product of the oxidation of formate by O2. Formate dehydrogenase appeared to be a membrane-bound enzyme. Of the possible physiological electron acceptors tested, only FAD gave rise to a detectable, although low, activity of formate dehydrogenase. Campylobacter sputorum grown in the complex medium with formate contained cytochromes of the b- and c-type. Cytochrome b was membrane-bound; cytochrome c was largely recovered in the soluble fraction. A CO-binding pigment was identified as a cytochrome of the c-type. Campylobacter sputorum possessed cytochrome c peroxidase activity. Cytochrome oxidases of a known type could not be detected unequivocally in a (reduced-plus-CO minus reduced) difference spectrum. An important role in the microaerophilic nature of C. sputorum is ascribed to H2O2.
- Received:
- Revised:
- Published Online:
© Society for General Microbiology 1980