Is it possible for an anaerobic bacterium to test positive for cytochrome c oxidase?

Yes, it is possible for an anaerobic bacterium to test positive for cytochrome c oxidase, although it is uncommon. Some anaerobic bacteria may possess cytochrome c oxidase as part of their metabolic pathways, particularly if they can utilize oxygen in specific conditions or if they are facultative anaerobes. However, most strict anaerobes typically do not have this enzyme since they do not utilize oxygen for respiration.