Reversion of L forms and spheroplasts of Proteus mirabilis.

Altenbern, Robert A. (U.S. Army Chemical Corps, Fort Detrick, Frederick, Md.). Reversion of L forms and spheroplasts of Proteus mirabilis. J. Bacteriol. 85:269-272. 1963.-Spheroplasts or 3-B type L forms of Proteus mirabilis formed by growth in the presence of penicillin are able to revert to the bacillary form, as judged by regain of resistance to osmotic shock. Reversion takes place in the absence of exogenous nutrients, although at a lesser rate than that observed in a nitrogen-rich medium. Either chloramphenicol or 6-azauracil can completely inhibit reversion of spheroplasts in a penicillin-free medium. By direct measurement, there was no detectable change in total protein content throughout the period of reversion of a spheroplast suspension. Assay for acid-insoluble diaminopimelic acid (DAP) revealed that a large part of the DAP of the cell wall of normal cells was lost when the cells were converted to spheroplasts by exposure to penicillin. Upon transfer to penicillin-free medium, there was a rapid increase in acid-insoluble DAP in the wall of the reverting spheroplast. When spheroplasts were transferred to penicillin-free medium containing chloramphenicol, the acid-insoluble DAP in the wall of the spheroplast continued to decrease. The significance of these results in regard to sites of activity of the antibiotics involved is discussed.