[Biochemical basis of varying nystatin resistance of Saccharomyces cerevisiae and Candida maltosa mutants].

Six groups of nystatin resistant mutants of C. maltosa and of haploid and diploid Saccharomyces cerevisiae strains were obtained with the help of genetic and biochemical analysis. It has been shown that every group of the mutants was characterized by a specific level of resistance to nystatin.

Sterol composition of nystatin-resistant Candida maltosa mutants.

Composition of sterol fractions of nystatin-resistant Candida maltosa strains was determined. Using UV-spectrometry, TLC and GLC-MS it was demonstrated that resistance to nystatin is connected with the composition alterations of yeast cell sterols. Block of different stages of ergosterol biosynthesis was revealed in some mutants, viz.

[The use of various mutagens for induction of nystatin-resistant mutants in Candida maltosa].

The mutagenic activity of nitrous acid, 6-N-hydroxylaminopurine, N-methyl-N'-nitro-N-nitrosoguanidine and 4-N-nitroquinoline oxide was studied for Candida maltosa. The efficacy of their action on C. maltosa cells was determinded in order to obtain nystatin-resistant strains.

[Study of the resistance of Candida guilliermondii to polyene antibiotics].

250 Candida guilliermondii strains resistant to the polyene antibiotics nystatin, levorin and amphotericin B were obtained using UV irradiation. When the mutant strains became resistant to one of the polyene antibiotics, their resistance to the other ones changed. Phenotypic analysis showed that the resistance of the strains to polyene antibiotics did not make them susceptible to a rise in osmotic pressure and to a change of the temperature of incubation.