Identification and distribution of genetic markers in three closely related taxa of the Mycoplasma mycoides cluster: refining the relative position and boundaries of the Mycoplasma sp. bovine group 7 taxon (Mycoplasma leachii)

Abstract

Mycoplasmas belonging to theMycoplasma mycoidesphylogenetic cluster are all important ruminant pathogens that are genetically closely related but differ in terms of severity and prevalence of the associated diseases. They are distributed among six taxa, the description of which has recently been amended. In the present study, DNA fragments that diverge between the type strains of three taxa were enriched using suppression subtractive hybridization. Of the three taxa, two were representative of the well-established speciesM. mycoidesandM. capricolum, while the third one,Mycoplasmasp. bovine group 7 (Mbg7), has only recently been proposed as a separate species,Mycoplasma leachii. Specific DNA fragments were further characterized by sequencing and used as markers to assess the genetic diversity within and between taxa. The data indicate that the selected markers are unequally distributed within their own taxon but also across taxa. The patterns observed suggest the occurrence of a genetic continuum of strains within theM. mycoidescluster that may compromise the boundaries between taxa and, in turn, diagnosis outcomes. ForMbg7, the overall nature and distribution of the markers indicate a rather homogeneous group that is distinct from theM. capricolumandM. mycoidesspecies and might be considered as a genomic chimera between these two species.