[Effect of oxygen concentration and the physiological state of cells on the respiration chain of Candida mycoderma]

The effect of oxygen concentration and limitation of the cultural growth by the substrate to be oxidized on the functionation of the respiration chain and the ratio of cytochromes a : c : b was studied in intact cells of Candida mycoderma. As the concentration of oxygen in the medium decreases and the growth of the culture slows down, the cyanide-resistant pathway of electron transport (CrPET), which is inhibited by benzhydroxamic acid, is found in the yeast cells. At the same time, the content of cytochrome a in the cells decreases, probably because cytochrome oxidase is now less involved in electron transport via CrPET, whereas the content of cytochromes c and b increases. The latter fact seems to be due to the activation of the cytochrome-c-peroxidase pathway of electron transport whose functioning in the studied strain of C. mycoderma has been shown earlier. CrPET was found to function also at a high concentration of oxygen, but under conditions of the transition of the culture to the stationary phase, as well as during the incubation of resting cells taken at the exponential phase of growth. The manifestation of CrPET in conditions of a low concentration of oxygen can be caused not only by the direct effect of its deficiency on the respiration chain, but also by a change in the physiological state of yeast cells at their growth decelerates or ceases.