Use of 5-fluorouracil for the isolation of auxotrophic mutants of Bacillus megaterium.

Wachsman, J. T. (University of Illinois, Urbana), and L. Hogg. Use of 5-fluorouracil for the isolation of auxotrophic mutants of Bacillus megaterium. J. Bacteriol. 87:1137-1139. 1964.-The combination of 5-fluorouracil (FU) and uridine was used to selectively kill wild-type cells of Bacillus megaterium KM, thereby providing surviving populations greatly enriched in auxotrophic mutants. Exponentially growing cells were irradiated with ultraviolet light, incubated in a basal medium containing sucrose and, in most experiments, a complete amino acid mixture. Exponentially growing cells were then washed and incubated in the basal medium containing only sucrose, to deplete intracellular reserves. FU and uridine were added, and incubation was continued. After 5 hr, auxotrophs may account for up to 50% of the survivors. Organisms requiring each of the following compounds were identified: alanine, arginine, asparagine, cysteine, histidine, phenylalanine, serine, threonine, tyrosine, adenine, and guanine.