[Effect of pH values of the medium unfavorable for growth on the physiological, morphological and cytological characteristics of a chemostat culture of Candida utilis].

The effect of growth inhibiting values of pH of the medium (pH 2.3 and 7.8) on physiological, morphological and cytological characteristics was studied with the chemostat culture of Candida utilis. Changes in the pH of the medium were accompanied with a decrease in the economic coefficient of the yeast cells, an increase in the respiratory quotient and the activity of phosphohydrolase. Phase-contrast micriscopy has shown that, at acid pH values, the cells were smaller than in the control (in the cells grown under optimal conditions) and rather uniform, oval or rounded, and contained large lipid granules. The presence of large lipid granules was confirmed by electron microscopy; vacuoles were smaller than in the control cells, but their number was greater than one; mitochondria stuck together and had one general outer membrane; the cell wall was 3--4 times thicker. At alkaline pH values of the medium, the whole cellular organization of C. utilis was disordered: the cells were larger, the size of vacuoles increased too much, and the structure became heterogeneous.