Guanine-Plus-Cytosine Compositions of and Deoxyribonucleic Acid Hybridization Comparisons between Mycoplasma hyopneumoniae and Mycoplasma flocculare

Among the mycoplasmal species commonly isolated from porcine lungs are Mycoplasma hyopneumoniae and Mycoplasma flocculare. The former organism is a proven agent of enzootic porcine pneumonia, whereas the latter organism is of little or no pathogenicity. These mycoplasmas show considerable antigenic cross-reactivity. The deoxyribonucleic acids of M. hyopneumoniae strain 11 and M. flocculare strain Ms42T (T = type strain) each had a guanine-plus-cytosine content of 33 mol%. We also determined the extent of deoxyribonucleic acid sequence homology as reflected in deoxyribonucleic acid-deoxyribonucleic acid hybridization values. Approximately 10% heterologous hybridization was observed. Thus, our data support the previous classification of these organisms as separate species within the genus Mycoplasma.