5-bromouracil utilization by Bacillus subtilis.

The replacement of thymine (T) in deoxyribonucleic acid (DNA) by 5-bromouracil (BU) (F. Weygand, A. Wacker, and H. Dellweg, Z. Naturforsch. 7b:19, 1952) is an aid in density separation of types of DNA, and in studies on radiobiology and mutagenesis. The usefulness of BU is, however, limited by its toxic effects. Extensive substitution in DNA of T by BU is lethal for most Escherichia coli and Bacillus subtilis strains. To decrease this toxicity, Oishi and Sueoka (Proc. Natl. Acad. Sci. U.S. 54:483, 1965) suggested adding T to BU-containing media. Because of an apparent heterogeneity