EXCRETION OF GLYCOLATE BY A SPECIES OF CHLORELLA (CHLOROPHYCEAE)1

The claim that Chlorella sp. (CCAP 211/8p), sometimes referred to as C. fusca, Shihira and Krauss, does not excrete glycolate has been reexamined. Chlorella sp. grown on 5% CO₂in air, excreted glycolate when incubated in light in 10 mM bicarbonate. Excretion ceased 30–60 min after transfer of the cells to air and no excretion could be detected with air-grown cells or with cells grown on 5% CO₂in media buffered at pH 8.0. Incubation with 10 mM isonicotinyl hydrazide, a glycolate pathway inhibitor, caused excretion in air-grown cells and stimulated excretion in CO₂-grown cells indicating that both the rate of glycolate synthesis and metabolism is higher in CO₂grown cells than in air-grown cells. Enhanced glycolate synthesis and excretion in CO₂-grown cells is correlated with law photosynthetic rate in 10 mM bicarbonate, and the photosynthetic rate of these cells doubles over a period of 2–2.5 h after initial transfer from high CO₂to bicarbonate. This correlation of photosynthetic induction with cessation of glycolate excretion is similar to that reported in a bluegreen alga and thought to occur in other green algae. These results indicate that glycolate excretion and its regulation in this species of Chlorella is not different from that in other algae.