Virulent Treponema pallidum: aerobe or anaerobe.

Substrate degradation and protein synthesis served as indicators of metabolism in virulent Treponema pallidum. Opitmal metabolic activity in these spirochetes was observed at 10 to 20% O2 concentrations, with markedly reduced activity at higher or lower O2 levels or under anaerobiosis; alternate functioning electron acceptors that might substitute for O2 were not found. Carbon monoxide and cyanide at concentrations that inactivate cytochrome oxidase were not effective metabolic poisons for T. pallidum, although Micrococcus lutea, a strict aerobe with cytochrome-dependent respiration, was inhibited under similar experimental conditions. Motility of virulent T. pallidum was vigorous in the presence of O2 and sluggish or inhibited in its absence, reinforcing the role of O2 in T. pallidum metabolism.