Histochemical study of oxidative and hydrolytic enzymes in the human thyroid

Auxotrophic mutants of Bacillus subtilis 168 that require either tryptophan, uracil, or thymine died rapidly when de- prived of any of these compounds. Phage PBS1 was produced by infected B. sub- tilis 168 (thy try-2) deprived of thymine. Phage PBS1 was not produced by in- fected B. subtilis 168 (try-2) deprived of tryptophan or infected B. subtilis 168-15 (try-2 ura) deprived of uracil. B. subtilis 168 thy try-2 and 168-15 could be trans- duced by phage PBS1 after prolonged deprivation of tryptophan or uracil, respec- tively. When B. subtilis 168-15 was transduced to uracil independence by phage PBS1, the uracil-independent transductants became immune to uracil-less death within 10 min of exposure to phage, and began to multiply within 2 hr after ex- posure to phage at an incubation temperature of 46 C.