A new sensitive test based on yeast cells for studying environmental pollution.

Different tests based on yeast cells were developed for determination of mutagenic/carcinogenic action; however, they all showed lower sensitivity compared to bacterial tests, the main reason for this being the limited permeability of yeast cells. We found that general permeability of Saccharomyces cerevisiae cells can be increased by mutation and on this basis we developed a more sensitive test. The aim of this study was to prove the applicability of our test, called D7ts1, in environmental studies.

Increased endocytosis in the Saccharomyces cerevisiae fragile mutant VY1160.

The VY1160 mutant is characterized by cell lysis in hypotonic solutions and generally increased permeability to substances for which Saccharomyces cerevisiae cells are not permeable. Two mutations, srb1 and ts1, have been identified in VY1160 mutant, and previous studies (Kozhina et al., 1979) have shown srb1 to be responsible for cell lysis.

Increased extracellular secretion in fragile mutants of Saccharomyces cerevisiae.

Evidences are presented for a generally increased extracellular secretion capability of the fragile mutants of S. cerevisiae. Proteins secreted in wild type yeasts to the periplasmic space can not be retained by the defective cell wall of the fragile cells and are released into the medium.

Relaxed mutant of Saccharomyces cerevisiae: proper maturation of ribosomal RNA in absence of protein synthesis.

We have characterized a relaxed yeast mutant, S. cerevisiae SY15, isolated by mutagenesis with ethylmethanesulfonate of strain A364A. Starvation for a required amino acid or treatment with cycloheximide blocks protein synthesis in both parental and mutant strains, while the synthesis of total RNA is inhibited by 72% in A364A and 23% in SY15 cells.