Definition of the blue mutant phenotype and its genetic basis inSaccharomyces cerevisiae

Abstract

SUMMARYMutant colonies of yeast are described which varied in colour from blue to green and in intensity of colour when grown on medium containing methylene blue. Blue mutant colonies contained more dead cells, decolorized redox dyes more slowly, had a higher respiratory quotient on glucose containing medium, and absorbed more methylene blue dye than did wild-type. The blue colony phenotype was induced both spontaneously and at high frequency by ultraviolet light and ethylmethane-sulphonate in both haploid and diploid strains. Many of the light-coloured colonies isolated following mutagenic treatment reverted to wild-type when subcultured but most dark-coloured colonies remained stable. Stable blue mutants were shown to arise by mutation of many separate nuclear genes in haploids and were often caused by recessive lethals in diploids.