The base compositions of the deoxyribonucleic acid (DNA) and ribo-nucleic acid (RNA) of three strains of Mycoplasma laidlawii and one of Mycoplasma mycoides var. mycoides have been determined. The adenine (A) + thymine (T) content of all the samples examined was much greater than the guanine (G) + cytosine (C) content, the values for % GC ranging from 34·4 to 32·5 for the sample of M. laidlawii to 30·0 for M. mycoides var. mycoides. The adenine + uracil/guanine + cytosine value for the RNA of all the samples was in the range 1·17–1·20.
The amino acid content of the protein of Mycoplasma laidlawii was also determined. This agrees closely with the values obtained by Sueoka (1961) for the amino acid composition of the protein for a bacterium having the same DNA base composition.
The values given in a previous communication (Jones, Tittensor & Walker, 1965) for the amino acid composition of the protein of Mycoplasma mycoides var. capri were incorrect since a protein fraction had precipitated from the medium during the growth of the organism because of the decrease in pH value of the culture which occurred. The correct values are now given and they agree closely with the values predicted from the work of Sueoka (1961).
JonesA. S.,
TittensorJ. R.,
WalkerR. T.1965; The chemical composition of the nucleic acids and other macromolecular constituents of Mycoplasma mycoides var. capri. J. gen. Microbiol 40:405
MorowitzH. J.,
TourtellotteM. E.,
GuildW. R.,
CastroE.,
WoeseC.,
CleverdonR. C.1962; The chemical composition and sub-microscopic morphology of Mycoplasma gallisepticum Avian PPLO 5969. J. molec. Biol 4:93
NeimarkH. C.,
PèneJ. J.1965; Characterization of pleuropneumonia-like organisms by deoxyribonucleic acid composition. Proc. Soc. exp. Biol. Med 118:517
SchildkrautC. L.,
MarmurJ.,
DotyP.1962; Determination of the base composition of deoxyribonucleic acid from its buoyant density in CsCl. J. molec. Biol 4:430
WyattG. R.,
CohenS. S.1953; The bases of the nucleic acids of some bacterial and animal viruses: the occurrence of 5-hydroxymethyl cytosine. Biochem. J 55:774