Abstract
Ten of 200 strains of Mycobacterium kansasii were found to produce very mucoid growth on Lowenstein-Jensen medium. By electronmicroscopy these 10 strains were found to be lysogenic, whereas no phage was observed in cultures of 30 non-mucoid strains. The cultural and biochemical properties of the lysogenic strains are compared with those of non-lysogenic strains, and the morphology of the phages is described.