Growth response of axenic Entamoeba histolytica to hydrogen, carbon dioxide, and oxygen.

Entamoeba histolytica required CO2 for growth in axenic culture while growth was inhibited by H2. The organism was tolerant to 5% O2 in the gas phase and it was able to detoxify products of O2 reduction in the medium. The ameba did not require a negative oxidation-reduction potential for axenic growth. However, little or no free O2 was present in media exposed to 5% O2 in the gas phase. Growth was improved by adding yeast extract to the medium.