Abstract
The nucleotide sequence of the 16S rRNA gene of Mycoplasma flocculare was determined and was compared with the sequence of a related porcine mycoplasma, Mycoplasma hyopneumoniae. While the overall level of DNA-DNA homology was approximately 11%, sequence alignment of the two 16S rRNA genes yielded a homology value of more than 95%, emphasizing the highly conserved nature of the 16S rRNA gene. Multiple sequence alignments with other mollicutes indicated that M. flocculare, M. hyopneumoniae, and Mycoplasma hyorhinis form a subcluster within the fermentans phylogroup, and this subcluster is distinct from the Mycoplasma pneumoniae phylogroup. Thus, the three mycoplasmas isolated from porcine respiratory systems exhibit phylogenetic similarities.