The effect of aminopterin (4-amino folic acid) on growth and cell division of fermentative versus oxidative yeasts

In a related brewing study detailed characteristics of fermentations displaying effective yeastaminopterin interaction were presented.Fermentative yeast types (certain Saccharomyces species and Selenotila intestinalis) proved effective aminopterin reactors whereas oxidative yeasts (certain Candida, Cryptococcus, Pichia, Rhodotorula, Saccharomyces, and Trigonopsis species) proved ineffective reactors. In general effective reactors were polyploids characterized by the lack of film or pellicle formation and ineffective reactors the opposite. In stationary fermentations the Fleischmann 139 strain of S. cerevisiae proved a fair reactor. When aerated it proved an ineffective reactor and aminopterin or products there-of stimulated growth. Conversely aeration enhanced aminopterin activity of effective reactor yeasts.The positive effect of biotin on aminopterin activity and the negative effect of yeast extract, L-asparagine, adenine and thymine is shown and compared and contrasted with earlier reported studies.These findings supported by outside data suggest that oxidative yeasts (and bacteria) can readily elicit enzymes capable of inactivating aminopterin whereas fermentative types are lacking in this capability. Finally that past yeast-aminopterin studies were conducted with oxidative yeast types.Advantages of effective aminopterin reactor yeasts to be published elsewhere include improved ultrastructure using KMnO₄–OsO₄ fixation, a yeast bioassay procedure for detecting aminopterin in plasma and urine, and cell synchronization.Non-Standard Abbreviation apt aminopterin