Mitomycin C isknowntobethemostefficient antibiotic whichinduces bacteriocins incertain mutantsof gram-positive andgram-negative bacteria (2). Although ithasbeenreported tobe bacteriocidal to mycobacteria (3),successful isolation ofbacteriocins fromthis genushasnot beenaccomplished. Duringourstudies onmutants isolated from various species ofmycobacteria, a mutantof Mycobacterium tuberculosis BCG wasfoundto produce bactericidal phage-like particles after mitomycin C treatment. TheBCG strain usedinthepresent study was originally obtained fromtheInstituto Nacional deTuberculosis, Caracas, andwasmaintained inaLowenstein-Jensen medium. A spontaneous mutantoccurred during cultivation at37C in Middlebrook 7H9 Broth(Difco) without enrichment. Thismutantstrain, characterized by shortrod-shaped cellscontaining acid-fast granules, grewmorerapidly invarious liquid media, suchasPenassay (Difco), Middlebrook, andDubos(Difco) broths, thandidtheparent strain. Itshowed smoothsurface colonies when grownonDubosOleic Agar(Difco) enriched with0.25%bovine serumalbumin fraction V (Sigma Chemical Co.,St.Louis, Mo.)and 0.75%dextrose. Ultrastructurall y,
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Imaeda et al. (1968) studied this question.