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Abstract
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).
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