Cleavage Patterns of the Mycoplasma Chromosome, Obtained by Using Restriction Endonucleases, as Indicators of Genetic Relatedness Among Strains

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Abstract
Purified deoxyribonucleic acids (DNAs) of representative strains of nine established serovars of the human mycoplasma Ureaplasma urealyticum and of five strains of Mycoplasma pneumoniae were digested with a variety of restriction endonucleases. The cleavage patterns obtained by electrophoresis of the digestion products separated the nine U. urealyticum serovars into two definite clusters, one consisting of serovars 1, 3, and 6 and the other consisting of serovars 2, 4, 5, 7, 8, and 9, in agreement with previous results obtained by electrophoresis of cell proteins and DNA-DNA hybridization. Although the five M. pneumoniae strains differed in virulence and adherence capacity, they exhibited similar DNA cleavage patterns, indicating a high degree of genetic homogeneity. The enzymes KpnI, XhoI, BamHI, and PstI, which possess guanine-plus-cytosine-rich recognition sequences, cleaved the DNA of U. urealyticum (guanine-plus-cytosine content, about 28 mol%) into a small number of fragments, whereas SmaI, with the recognition sequence CCC/GGG, failed to cleave U. urealyticum DNA into visibly distinct fragments. The same restriction enzymes produced multiband cleavage patterns with M. pneumoniae DNA, which has a guanine-plus-cytosine content of about 40 mol%. Restriction endonucleases EcoRI, HindIII, HpaI, and XbaI, which have recognition sequences rich in adenine plus thymine, produced multiband patterns with the DNAs of both U. urealyticum and M. pneumoniae. We concluded that the cleavage patterns of mycoplasmal DNAs digested with restriction endonucleases provide a means for determining genetic relatedness among mycoplasmas.

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