THE PROPHAGE OF SPßc2dcitK₁, A DEFECTIVE SPECIALIZED TRANSDUCING PHAGE OF BACILLUS SUBTILIS

Richard Rosenthal ¹, Patryce A. Toye ¹, Ruth Z. Korman ¹, and Stanley A. Zahler ¹

¹ Division of Biological Sciences, Cornell University, Ithaca, New York 14853

The defective specialized transducing phage SPßc2dcitK₁ carries two known bacterial genes, kauA and citK, as well as SPß phage markers including the heat-sensitive repressor allele, c2. Some phage genes (including essential ones) are missing. When SPßc2dcitK₁ transduces SPß-sensitive cells of Bacillus subtilis, the defective prophage is inserted into sites in the homologous bacterial DNA of the attSPß-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 (Campbell 1962) circular phage genome may occur transiently. If the transductants are superinfected by SPßc2 or by the clear-plaque mutant SPßc1, the resulting double lysogen can be heat induced to release high-frequency-of-transduction (HFT) lysates for kauA and citK.

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