PROPHAGE OF SP-BETA-C2DCITK1 - DEFECTIVE SPECIALIZED TRANSDUCING PHAGE OF BACILLUS-SUBTILIS

Abstract

The defective specialized transducing phage SP.beta.c2dcitK1 carries 2 known bacterial genes, kauA and citK, and SP.beta. phage markers including the heat-sensitive repressor allele, c2. Some phage genes (including essential ones) are missing. When SP.beta.c2dcitK1 transduces SP.beta.-sensitive cells of B. subtilis, the defective prophage is inserted into sites in the homologous bacterial DNA of the attSP.beta.-kauA-citK region of the recipient chromosome. During the growth of these transductants, occasional excisions occur that result in the loss of the phage genes and of the heterogenotic state. These excisions increase greatly in frequency during growth at repressor-inactivating temperatures. The kinds of insertions and excisions seen suggest that a Campbell-type circular phage genome may occur transiently. If the transductants are superinfected by SP.beta.c2 or by the clear-plaque mutant SP.beta.c1, the resulting double lysogen can be heat induced to release high-frequency-of-transduction (HFT) lysates for kauA and citK.