由DL-5-苯乙内酰脲酶法生产D-苯甘氨酸的菌种选育

本实验以假单孢菌Pseudomonas SP.27为出发菌株由DL-5-苯乙内酰脲发酵生产D-苯甘氨酸。野生菌产量为15.85μg/ml.首先对其进行紫外诱变处理1min,筛选出菌株Q_6,其产量为256.7μg/ml.然后用Q-6制备球形体,进行亚硝基胍诱变处理60min,得到Q_(68)菌株,其产量为453.4μg/ml.     

Rapid genetic test for discrimination between haploid and polyploid transformants in Saccharomyces

Summary Spheroplast fusion induced by polyethylene glycol often occurs during transformation of yeast spheroplasts. It leads to the appearance of polyploid transformants. We have developed a method of discriminating between haploid and polyploid transformants, based on qualitative comparison of the frequency of mitotic homozygotization for a recessive marker, lys2, in diploid and polyploid hybrids of transformants crossed with a tester haploid bearing lys2.We have used this method to compare the frequency of appearance of polyploids during transformations of spheroplasts and of intact cells using lithium chloride in the strain DC5. Polyploids constitute from 15% to 74% of transformants after transformation of spheroplasts. In lithium chloride transformation polyploids arose in only one of four experiments and constituted 9% of transformants.     

UV-induced instability in Candida albicans hybrids

Summary Auxotrophic variants were obtained following UV-irradiation of Candida albicans hybrids which were heterozygous (+/+/-/-/) for various genetic markers (met, ade, his, lys). Some variants contained less DNA (per cell) than did the hybrids from which they originated; such variants were considered to arise in a process which resulted in generalized reduction in ploidy. These results provide the basis for a cyclic parasexual system (2n × 2n 4n 2n) for genetic analysis in this amictic diploid species.