THE ASSAY OF NITRATE REDUCTASE IN WHOLE CELLS OF CHLORELLA: STRAIN DIFFERENCES AND THE EFFECT OF CELL WALLS

SUMMARY Strains of Chlorella with a sporopollenin-like layer in their cell-walls differ from strains without this layer in that their chlorophyll is extracted poorly by ethanol and they fail to stain with aniline blue. Exogenous NADH is not used as an election donor for nitrate reduction by frozen/thawed organisms having this layer and it is concluded that the layer impedes the passage of NADH; malate, which presumably reduces NADH held within the cell walls, is an effective electron donor for nitrate reduction. Frozen/thawed organisms of strains without this layer in their walls reduce nitrate when NADH is added. All the tested strains with this layer and the associated properties have been classified on other criteria as belonging to C. fusca var. vacuolata; the other strains examined have been classified as C. vulgaris or C. saccharophila.