Lactoflavin in micro-organisms

An antimycin A- and cyanide-resistant variant of Candida utilis arising during copper-limited growth

1. During copper-limited growth of Candida utilis in continuous culture on a non-fermentable carbon and energy source there is a selective pressure favouring the emergence of variants that are less dependent on copper. 2. We describe the properties of such a variant that by-passes cytochrome oxidase (EC 1.9.3.1) by utilizing an alternative oxidase communicating with the respiratory chain at about the level of cytochrome b. 3. Both direct studies of isolated mitochondria and calculations based on growth parameters showed that only one of the normal three phosphorylation sites was active. This site was localized between NADH and the cytochromes. 4. Growth of the variant with copper-supplemented media resulted in the return of cytochrome oxidase but not the loss of the alternative oxidase. 5. The alternative oxidase is inhibited by substituted benzhydroxamic acids. 6. Submitochondrial particles from the variant did not exhibit any novel electron-paramagnetic-resonance-spectroscopy features at about g=2.0 either at 80 degrees K or 12 degrees K.

A ction of cycloheximide on Zygosaccharomyces soja

Tsukada, Yoji (Kyoto University, Kyoto, Japan), Tsunetake Sugimori, Kazutami Imai, and Hideo Katagiri. Action of cycloheximide on Zygosaccharomyces soja. J. Bacteriol. 83:70-75. 1962.-Cycloheximide is known to inhibit the growth of some species of Saccharomyces and other fungi. A new type of action of this antibiotic, with Zygosaccharomyces soja as the test organism, is described in this paper. Growth of Z. soja was completely inhibited under aerobic conditions by cycloheximide in concentrations of more than 5 mug per ml of culture solution. Continued shaking of the culture for more than 96 hr in the presence of an inhibitory amount of cycloheximide restored growth, accompanied by the excretion of riboflavin to the extent of 30 mug per ml of culture solution. In the cells recovering from cycloheximide inhibition, the type of glucose metabolism differed from that in the mother strain; a respiratory quotient of 4 with the mother strain fell to 1 in the progeny. Glucose metabolism (O(2) uptake and CO(2) evolution) by resting cells was investigated, and it was concluded that inhibition of glycolysis was not significant. This was verified by comparing various dehydrogenase activities in the cell-free extract. There were essentially no differences between riboflavin-forming and nonriboflavin-forming cells. The presence of the hexose monophosphate shunt was deduced from the fact that glucose-6-phosphate dehydrogenase activity was the strongest of the various dehydrogenase activities.