Characterization of chromate-sensitive and-tolerant mutants ofSchizosaccharomyces pombe

Stable chromium(VI)-sensitive and -tolerant mutants were obtained by induced mutagenesis ofSchizosaccharomyces pombe lysine and leucine auxotrophic heterothallic strains6chr+ and9chr+. Eleven of them were selected for further studies. Fast transport of51CrO42− was detected in a representative sensitive mutant,chr-51S, while the tolerant mutantchr1-66T and the parental strain6chr+ exhibited significantly lower51CrO42− uptake. The segregation of tetrads of three selected CrVI-tolerant mutants,chr1-66T, chr1-14T andchr2-04T, strongly indicated that tolerance was determined by single mutations. Random spore analysis proved that the mutations ofchr1-66T andchr1-14T were allelic and the mutation of mutantchr2-04T was not allelic with the mutation ofchr1-66T. Recombinants carrying theura4D18 selective marker were created for transformation experiments. Two of them (chr1-661T andchr2-046T) can be used to clone and identify the genes responsible for their CrVI tolerance phenotype.