[Study of the sequential stages of Proteus vulgaris L-transformation by scanning electron microscopy]

Consecutive stages of L-transformation caused by penicillin in Proteus vulgaris were studied, from spheroplasts and unstable, easily reversing L-forms to stable L-forms which did not reverse. To maintain natural topography of the culture on the growth medium, millipore filters were placed on the surface of the medium and then were fixed with the culture. All the main elements of L-cultures were found at the stage of spheroplast formation, before the first passage onto the medium for cultivating L-forms, i.e. spherical cells having a diameter from 3.5 to 1 mcm, elementary bodies 1.0-0.6 mcm large, filamentous structures with a diameter to 4 mcm, large bodies having dimensions of 20 mcm and more, and "cell-free" masses. The composition of the structural elements and their reproduction are supposed to be almost the same in the bacterial culture and L-forms at the stage of spheroplast formation.