Trichomonas vaginalis requires traces of oxygen and high concentrations of carbon dioxide for optimal growth

Abstract

The effects of O 2 and CO 2 on the growth in culture of Trichomonas vaginalis strain C1-NIH were investigated. Growth under pre-purified N 2 in the absence of CO 2 supplementation gave a doubling time of 4.4 h; when traces of O 2 (< 0.25 μM) were present, the doubling time was 3.5 h. Organisms grew most rapidly (doubling time 2.3 h) with traces of O 2 (< 0.25 μM) and with the CO 2 level controlled at 5 mM. The balance of fermentation products from maltose was greatly influenced by supplied gases. Under strictly anaerobic conditions at 5 mM CO 2, equimolar glycerol and lactate accounted for more than 95% of the measured products, whereas lower CO 2 increased acetate production. Under microaerobic conditions (O 2 < 0.25 μM) acetate was the major product when CO 2 was limited to that evolved endogenously; again 5 mM CO 2 favoured glycerol and lactate production. Activities of key enzymes measured in cell-free extracts (pyruvate:ferredoxin oxidoreductase, hydrogenase, glycerol kinase, malate dehydrogenase (decarboxylating) and lactate dehydrogenase) altered with growth conditions commensurately with observed changes in metabolic flux patterns. These results suggest that T. vaginalis is optimally adapted to conditions it experiences in situ in the vagina (traces of O 2, high CO 2).