- Volume 113, Issue 1, 1979

The denaturation map of Eco RI-digested pCR11, a ColE1-Km plasmid, is described. The 2·0 kilobase ColE1-derived segment contains an adenine + thymine rich site in the colicin immunity gene region. In the 7·2 kilobase kanamycin resistance region, the transposon Tn903 consists of an adenine + thymine rich 0·98 kilobase kan gene region flanked by a guanine + cytosine rich 1·09 kilobase inverted duplication.

Changes in the cellular content of glucose 6-phosphate and storage carbohydrates during catabolite derepression were measured during the diauxic growth of Saccharomyces cerevisiae on glucose (1 %, w/v) medium. After the exhaustion of glucose there were transient increases in glucose 6-phosphate, alkali-soluble glycogen and trehalose, reflecting enhanced gluconeogenesis, followed by an increase in acid-soluble glycogen. During the subsequent adaptation to growth on ethanol the amounts of glucose 6-phosphate, trehalose and glycogen returned to basal levels. Thus storage carbohydrates, of which glycogen is quantitatively the most important, appear to act as the energy source for catabolite derepression.

Although contents of triacylglycerols, free sterols and esterified sterols did not alter during the 3·5 h cell cycle of Candida utilis NRRL Y-900 growing synchronously under glucose limitation, changes were detected in the phospholipid content. Phospholipid:sterol molar ratios were lowest in organisms sampled after 2·5 h and highest in those analysed after 0·5 h of the cycle.

Treatment of whole yeast cells with a mixture of a reducing agent and 1,3-β-glucanase isolated from Basidiomycete QM806 led to the production of sphaeroplasts from ascomycetes, from some fungi imperfecti, but not from basidiomycetes. Association of 1,3-β-glucanase with a second enzyme, 1,4-α-glucanase, from Trichoderma viride, was required for sphaeroplast release from some, but not all, basidiomycetes and fungi imperfecti. The ability of yeast cells to liberate sphaeroplasts following appropriate enzymic treatment is proposed as a taxonomic criterion for differentiating basidiomycetous from ascomycetous yeasts and for classifying fungi imperfecti yeasts.