It was found that “auto-plaques” were produced without addition of any indicatorstrain on the lawn of Myc. Jucho, which was preliminarily lysogenized by Y 13 L phage, subcultured on Ogawa's egg slant and seeded on agar plate, and that the bacterial growth was inhibited in the same time, on the similarly seeded agar plate with the same Mycobacterium, by spotting a phage suspension of Y 13 L. However, no plaquewas produced on agar plate or Ogawa's egg plate seeded with the same bacterial culture maintained on agar media.
Turbidity of the “auto-plaque” depended on the culture age of the lysogenic strainof Ogawa's egg slant from which bacterial suspension seeded was prepared, namely, the older became the culture, the clearer became the plaque.
Addition of Calcium chloride at a cencentration of 2x10
-3 Moliml to Ogawa's madia, on which the bacteria was subcultured, inhibited the “auto-plaque” formation completely.
Analytical studies suggestedthat the “auto-plaque” and “dismune” phenomena described above were produced by neither a virulent mutant from Y 13 L phage nor a sensitive mutant population derived from lysogenic Jucho.
The number of colonies produced on Ogawa's egg plate by seeding a bacterial suspension of the lysogenic Jucho prepared from Ogawa's slant was about three times as much as that of the agar plate.
These investigations seem to suggest thepossibility of phage induction of lysogenic Jucho strain by changing the culture media from Ogawa to agar.
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