EFFECT OF NYSTATIN ON THE UTILIZATION OF SUBSTRATES BY YEAST AND OTHER FUNGI

Nystatin2 is one of a group of polyene antifungal antibiotics discovered in recent years (Hazen and Brown, 1951; Oroshnick et al., 1955). It contains a conjugated tetraene grouping and a diene unit, a carbonyl and a primary amino group, and has a molecular weight of approximately 950 (Dutcher et al., 1955). Nystatin inhibits the growth of most fungi at concentrations between 1 and 10 jig per ml, but shows no activity against actinomyces, bacteria, rickettsiae, or animal cells. It is more effective against vegetative cells than against spores. Its antifungal action is not prevented by casein hydrolyzate or yeast extracts, nor is it affected by pH over a fairly wide range. Its activity is reduced in 0.01 M cysteine solution (Donovick et al., 1955) and in 30 per cent plasma (Pagano and Stander, 1955). Its action appears to be primarily fungicidal and irreversible. The development of organisms resistant to high concentrations of nystatin has not been observed either in clinical use or in laboratory studies. It has, however, been possible to obtain from a few fungi mutants for which the growth inhibiting concentration of nystatin is several times that required for the original strains (Stout and Pagano, 1955-1956). Dr. Harlyn 0. Halvorson observed that the aerobic and anaerobic utilization of glucose and maltose by Saccharomyces cerevisiae was inhibited in the presence of low concentrations of nystatin. The experiments presented here represent an extension of this initial observation.