A 41-kDa variable surface protein of Mycoplasma gallisepticum has a counterpart in Mycoplasma imitans and Mycoplasma iowae

Mycoplasma gallisepticun, M. imitans and M. iowae are three morphologically similar avian Mycoplasma species, and M. gallisepticum and M. imitans have been shown to be antigenically related. Using a monoclonal antibody that binds to the previously described size- and phase-variant integral membrane surface protein PvpA of M. gallisepticum, we have identified in all three avian Mycoplasma species a 41-kDa surface antigen, which in M. gallisepticum and M. imitans was identified as peripheral membrane protein undergoing variation in expression among clonal isolates. Southern blot analysis using the pvpA gene as a probe demonstrated sequence homology with M. imitans and M. iowae genomic DNA and suggested that a pvpA-related gene that may encode the 41-kDa product exists in these two Mycoplasma species. These studies establish (i) that M. iowae is antigenically related to M. gallisepticum and M. imitans, (ii) that the three species share non-ribosomal gene sequences, and (iii) that peripheral membrane proteins contribute to Mycoplasma surface variation.