Effect of reducing agents, catalase, and reuse of medium on toxicity of media for growth of Ureaplasma urealyticum.

The effects of catalase and reducing agents on the growth of Ureaplasma urealyticum type VIII in broth cultures were studied, and used medium was examined for the presence of toxic factors. Growth of U. urealyticum was slower in aged or pre-aerated medium than in fresh medium, although equivalent final yields were achieved. Generation times were 2.9 hr in pre-aerated broth and were 1.34 hr in pre-aerated broth supplemented with either 2mM dithioerythritol or catalase (300 units/ml). Growth and death of U. urealyticum in cultures rendered the broth medium deficient for growth when reinoculated. Filtration of spent medium, adjustment of pH, addition of urea, and reinoculation permitted growth at the same rate and to the same titer as that observed in unused medium. Omission of filtration allowed growth but the final yield was less than that in filtered medium. Addition of sonicated dead cells to filtered, supplemented, spent medium also resulted in only poor growth. Therefore, spent medium appears toxic because it contains organisms (either while or disrupted) that hydrolyze the urea added and again render the medium deficient for growth by depleting an essential growth factor.