A comparison of two strains of the anaerobic ciliate Trimyema compressum

Two strains of the anaerobic ciliate Trimyema compressum, isolated from different habitats, were compared. The cytoplasm of the ciliates contained hydrogenosome-like microbodies and methanogenic bacteria; the latter were lost during continued cultivation. In addition both strains harbored a non-methanogenic endosymbiont, which was lost in strain K. The ciliates lacked cytochromes, cytochrome oxidase and catalase but contained superoxide dismutase. Hydrogenase activity could be demonstrated only in strain N. In monoxenic culture strain K needed sterols as growth factors. The cells of both strains reacted similarly with respect to oxygen tolerance (up to 0.5 mg O₂/l), inhibition of growth by cyanide and azide, and resistance to antimycin A. Only cells of strain N showed growth inhibition by chloramphenicol. It is concluded that Trimyema compressum is an anaerobic, microaerotolerant organism, its microbodies show more resemblance to hydrogenosomes than to mitochondria.