In cultures of E. histolytica-organism t and E. histolytica-A. aerogenes the production of carbon dioxide, measured in Eldredge-tubes, was greater than could be calculated on the basis of glucose disappearing and lactate produced. The results appear to indicate that some glucose which could not be measured was derived by diffusion from the solid phase of the medium, and from fragmentation of rice flour with hydrolysis of the starch thus liberated. The possibility that some of the carbon dioxide may have been derived from protein and/or fat could not be ruled out. The excess of carbon dioxide in cultures with amebas over that produced by the respective bacterial symbionts without amebas was attributed to production of sugar by the amebas and utilization thereof by the bacterium but some of the gas may have been produced by the amebas.
Lactate, pyruvate, and 3-phosphoglyceric acid provided substrates for growth of A. aerogenes in pure culture, but in cultures of E. histolytica-A. aerogenes there were factors that could not be analyzed.
E. histolytica was shown to produce amylase which finds its way into the medium by unknown pathways. Amylase was demonstrated in overlay removed from cultures of E. histolytica-organism t when growth of organisms was inhibited by toluene. Quantitative data on activity of amylase were obtained from extracts of precipitates by acetone of ameba-harvests. The best extracts showed a specific activity of 48.4 units of amylase per milligram of protein. The activity was highest in the presence of sodium chloride, and optimum activity occurred somewhere between pH 5 to 6.