NITRITE ASSIMILATION BY THE YEAST CANDIDA-NITRATOPHILA

Nitrite uptake in the nitrate-assimilating yeast, Candida nitratophila , was inhibited completely by addition of nitrate or ammonium to cultu res at pH 8.0. Nitrite assimilation in these cultures was also complet ely dependent on the availability of a suitable carbon source (glucose ). In cultures at pH 5.0, neither nitrate nor ammonium inhibited nitri te uptake completely. In these cultures, some nitrite was assimilated in the absence of a carbon source. Carbon-deficient cultures at pH 5.0 were able to reduce nitrite to ammonium but excreted this ammonium wi thout further assimilation. Evidence for the uptake of nitrite by pass ive diffusion and by active transport via the nitrate uptake system is discussed.