Adaptive Changes in the Acetate Metabolism of Euglena*

SUMMARY. The acetate metabolism of Euglena grown on ethanol at pH 3.5 (Et‐grown) differs from that of the same strain grown on acetate at pH 7.3 (Ac‐grown) in several respects. Et‐grown cells have a rate of acetate oxidation at pH 7.0 lower than that of Ac‐grown cells. The rate of acetate oxidation by Et‐grown cells is markedly increased at low pH, whereas that of Ac‐grown cells is relatively independent of pH. At pH 5.5, the respiratory rate of Et‐grown cells can be increased by increasing acetate concentrations up to 18.4 IBM, whereas that of Ac‐grown cells is independent of acetate concentration above 4 mM. At pH 7.0, both types of cell are unaffected by changes in acetate concentration above 4 mM. Et‐grown cells incubated in the presence of acetate for about 80 minutes frequently adapt to acetate, taking on characteristics similar to those of Ac‐grown cells.