Abstract
The sizes of the genomes of 12 Ureaplasma strains isolated from six mammalian and one avian species, as determined by pulsed-field gel electrophoresis, varied from 760 to 1,170 kilobase pairs (470 to 723 megadaltons); and these values encompassed the values for the genomes of Ureaplasma urealyticum strains. Variation of at least 54% in the genome sizes restricts the usefulness of this taxonomic criterion for the genus Ureaplasma.