Studies on the minimum reproducible unit of staphylococcal L-forms.

The minimum size of a reproducible unit of staphylococcal L-forms was determined by filtration and electron microscopic methods. Ultrathin sections of an induced strain of Staphylococcal L-forms (STA-EMT-1) in liquid medium revealed several types of structures, all of which were bound by a single membrane and most of which possessed ribosome-like granules. Many of the small granules were less than 0.3 micron and were attached to the membrane of the large bodies. Using a serial filtration method, it was observed that viable L-forms were still detected in 0.22 micron filtrate, but the viable cell count of L-forms decreased in number with the decrease in pore size of membrane filters. A fractionation technique, using L-forms filtered through a membrane filter with a 0.45 micron pore size, revealed that there were three classes of small bodies but only the first class with ribosome-like granules over approximately 0.2 micron in diameter seems to be able to reproduce.