Determinations on the numbers of amebae obtainable from cultures of E. histolytica with 17 individual species of bacterial symbionts in whole-egg medium showed differences ranging from 20,000 to 450,000 amebae per culture.
E. histolytica-organism t could not be propagated through indefinite serial transfer in egg white medium even with enrichments of cholesterol and B vitamins. With enrichment of cholesterol the ameba was propagated in egg white medium with Escherichia coli and Aerobacter aerogenes, respectively, through indefinite serial transfer.
Evidence was obtained indicating that E. histolytica produces a gelatinase and/or a protease that liberates starch grains from particles of ground rice, and that rice proteolysis may be adaptive.
Using the Eldredge-tube method of measuring carbon dioxide, more of the gas was demonstrable from cultures of E. histolytica with two bacterial symbionts than from the symbiont alone except when glucose-enriched medium was used. The increase was attributable to substrate furnished through the metabolism of the amebae. No differences in production of carbon dioxide were demonstrable from cultures of E. histolytica-Clostridium perfringens, and of C. perfringens without amebae. This result was attributed to utilization of rice flour by C. perfringens.