A Study of the Control of Glycolate Excretion in Chlorella

Abstract

Chlorella pyrenoidosa cells grown on 5% CO₂ excreted glycolate when incubated in light with 10 mm bicarbonate, but excreted no glycolate under the same conditions when they were maintained on air for 7 hours prior to the assay. Incubation of 5% CO₂-grown and air-grown cells with 10 mm isonicotinyl hydrazide or 10 mm α-hydroxypyridinemethane sulfonate during the assay stimulated the excretion of glycolate by CO₂-grown cells severalfold that of air-grown cells.

Adaptation of CO₂-grown Chlorella to growth on air did not affect the levels of glycolate dehydrogenase in the cells and did not affect the rate of dark oxidation and metabolism of exogeneous ¹⁴C-glycolate by the cells. These results indicate that the lack of glycolate excretion by air-grown or air-adapted cells of Chlorella cannot be explained by a concomitant change in the level of glycolate dehydrogenase.