Relationship between Sugar Utilization and the Action of Cycloheximide on Diverse Fungi

Abstract

CYCLOHEXIMIDE (‘Actidione’, Upjohn) is an antibiotic which inhibits growth of protozoa¹, mammalian cells² and many fungi³. It has been proposed that cells having strong aerobic fermentative capability are especially sensitive to this antibiotic⁴. In the present work, oxygen consumption and aerobic carbon dioxide evolution by 17 fungi grown in glucose medium was measured by standard manometric techniques⁵. Drug sensitivity was determined by the tube-dilution method. No correlation was found between respiratory quotient and susceptibility to cycloheximide (Table 1). Respiration and fermentation of glucose by Saccharomyces pastorianus were not inhibited appreciably by 2 µgm. cycloheximide/ml. although 0.5 µgm./ml. halted growth. Cells of S. pastorianus fermented maltose when cultivated in maltose medium, but not when cultivated in glucose medium. Fermentation by maltose-adapted cells was not retarded significantly by 2 µgm. antibiotic/ml. but the inductive process was suppressed completely (Table 2). Cells exposed to the drug were still viable at the end of the experiment. Cycloheximide does not inhibit significantly activity of glycolytic enzymes but does prevent new enzyme synthesis. Protein or nucleic acid synthesis, therefore, seems to be one vulnerable site of cycloheximide action⁶.