Presence of viruses in a strain of mycoplasma pulmonis.

Filtrates prepared from heavily grown agar cultures of M. pulmonis strain Negroni-52 formed plaques on lawns of A. laidlawii strain JAl but not on those of M. pulmonis strains Ash or Negroni-52. The plaque-forming agent proved to be rod-shaped particles morphologically identical with mycoplasmavirus group 1. Evidence supporting the conclusion that the virus originated from Negroni-52 has been obtained. Electron microscopy revelaed that Negroni-52 is also a carrier of long-tailed phage-like particles.