Some characteristics of lysogens of Mycobacterium smegmatis.

By the use of radioactive labelling it was observed that mycobacteriophage butyricum (By) enter Mycobacterium smegmatis strain Rabinowitz (M. sm. R.) cells, lysogenise them but do not form plaques. Mycobacteriophage Rabinowitz (V72) and phage By proved to be heteroimmune; that is, they superinfect lysogens of one another productively. Spontaneous lysis frequencies of two different mycobacterium strains lysogenised by phage By [M. sm. R. (By); M. sm. b. (By)] and that of the double lysogenic M. sm. R. (V72, By) strain were compared. The spontaneous lysis frequency of the two monolysogenic strains was found to be similar (10(-4)-10(-2) indicating that transition into the vegetative replication cycle of By phages occurs also in M. sm. R. cells. Spontaneous lysis frequency of the double lysogenic strain was found to be influenced by the medium used.