The Chemical Composition of the Nucleic Acids and the Proteins of Some Mycoplasma Strains

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Abstract
The base compositions of the DNA and RNA of 3 strains of Mycoplasma laidlawii and 1 of M. mycoides var. mvcoides were 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 fron 34.4 - 32.5 for the sample of M. laidlawii to 30.0 for M. mycoides var. maycoides. The A + uracil/G+C value for the RNA of all the samples was in the range 1.17-1.20. The amino-acid content of the protein [degree]f M. laidlawii was determined. This closely agrees 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 previously given for the amino-acid composition of the protein of M. mycoides var. caorl 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. The correct values closely agree with the values predicted from the work of Sueoka (1961).