when treated with 365-nm radiation , cells of a wp2s strain ( a derivative of b/r transduced to his-4 ) plated on semi-enriched medium prepared with casamino acids did not yield induced mutations , whereas plating on semi-enriched medium prepared with nutrient broth did yield mutants at both the his-4 and trp loci at frequencies at least an order of magnitude lower than that observed with far-ultraviolet light .
C0007634
cells
C1708726
loci