Double lysogeny of Mycobacterium smegmatis.

While the plating efficiency of mycobacteriophage butyricum (By) on Mycobacterium smegmatis strain Rabinowitz (M.sm.R.) cells is less than 10(-8), it proved to be 5 X 10(-1) on the lysogenic Mycobacterium smegmatis strain Rabinowitz (M.sm.R. [V72]) cells. Bacteriophage By forms plaques on M.sm.R. cells at a very low frequency; it can, however, adsorb to these cells in the same degree as to its original host. The average burst size of Mycobacterium smegmatis strain butyricum (M.sm.b.) cells infected with mycobacteriophage By is 60, and that of M.sm.R. (V72) superinfected with bacteriophage By is only 6. A double lysognic strain was isolated from M.sm.R. (V72) cells surviving By phage infection.