Constancy of Deoxyribonucleic Acid Base Composition in the Transition of Sphaerophorus Necrophorus from Bacilli to Large Bodies.

Controversy exists concerning the relation or distinction of pleuropneumonia-like organisms (PPLO) and L-type erganisms (Smith, Bacteriol. Rev. 28:97, 1964). While some feel that PPLO and L organisms may be identical, i.e., that PPLO are stabilized forms derived from bacteria (Barile et al., Oral Surg. Oral Med. Oral Pathol. 16:1395, 1963), others recognize sufficient differences to warrant placing the PIPLO in the genus Mycoplasma (Klieneberger-Nobel, Pleuropneumonia-Like Organisms (PPLO) Mlycoplasmataceae, Academic Press, Inc., New York, 1962). Determination of deoxyribonucleic acid (DNA) base composition of bacterial cells shows promise as an aid in microbial taxonomy (Marmur et al., Ann. Rev. Microbiol. 17:329, 1963). Little is known about the DNA base composition of L organisms or l'l'LO. If it could be presumed that the DNA composition of a given bacterial species remains constant throughout transition to L organisms, then DNA base ratio analyses would be useful in the characterization of L forms and PPLO. Sphaerophorus necrophorus (Bacteroides funduliformis) is one of the few bacteria which provides a model system for this transition, since it spontaneously gives rise to L forms in appropriate media. The constancy of per cent guanine plus cytosine (% G +C), as determined