Ethanol inhibition of D-xylulose fermentation by Schizosaccharomyces pombe

Summary The kinetics of the utilization of D-xylulose by the yeast Schizosaccharomyces pombe has been examined under anaerobic batch conditions. The inhibitory effect of ethanol on xylulose uptake and ethanol production was studied at pH 6.0 and 30°C. Ethanol had little or no effect on the sugar uptake rate, but end product inhibition was observed on ethanol production. This non-competitive inhibition was linear with respect to ethanol concentration between 0 and 60 g/l. A kinetic model for the alcoholic fermentation of xylulose is presented.     

Radiation resistance in Schizosaccharomyces pombe

The fission yeast Schizosaccharomyces pombe serves as an excellent alternative and complementary model system for the analysis of genes and gene products involved in DNA repair. This brief review outlines the advantages of S. pombe and describes the radiation-sensitive mutants available for the analysis of DNA repair and recombination mechanisms in this organism. The progress in the cloning and characterization of representative genes is also described.     

Mutant enrichment of Schizosaccharomyces pombe by inositol-less death.

Enrichment procedures, such as those utilizing inositol-less death, have proven to be extremely powerful for increasing the efficiency of identification of spontaneous mutants in a variety of procaryotic and eucaryotic organisms. We characterized inositol-less death in several widely used strains of the inositol-requiring yeast Schizosaccharomyces pombe and determined conditions under which this phenomenon can be used to enrich for mutants. Conflicting reports in the literature on the effects of inositol starvation upon viability of S. pombe had cast doubt on the suitability of using inositol-less death in a mutant enrichment procedure for this organism. We determined that inositol-less death was strain dependent, with differences in viability of up to 5 orders of magnitude observed between the most-sensitive strain, 972, and the least-sensitive strain, SP837. Inositol-less death was also dependent upon the cell concentration at the time of initiation of starvation. While inositol-less death occurred at all four temperatures tested, the kinetics of death was slower at 16 degrees C than at 23, 30, or 37 degrees C. Inositol-less death was observed during growth in fermentable and nonfermentable carbon sources, although loss of viability in glycerol-ethanol was significantly slower than that in glucose, sucrose, or raffinose. The feasibility of exploiting inositol-less death to enrich for spontaneous mutants was demonstrated by the identification of amino acid auxotrophs, nucleotide auxotrophs, carbon source utilization mutants, and temperature-sensitive mutants. By varying starvation conditions, some mutants were recovered at frequencies as high as 5.7 x 10(-2), orders of magnitude higher than the spontaneous mutation rate.