GENETIC-VARIATION AMONG MYCOPLASMA-AGALACTIAE ISOLATES DETECTED BY THE VARIANT SURFACE LIPOPROTEIN GENE (VSPA) OF MYCOPLASMA-BOVIS

Multiple restriction fragments, homologous to the previously described Mycoplasma bovis vspA gene, were identified in the chromosome of Myco plasma agalactiae. The vspA, a representative variable surface lipopro tein gene of the vsp gene family, and four synthetic oligonucleotides, representing sequences complementary to selected regions of the vsp g enes, were used as probes against digested chromosomal DNAs of several M. agalactiae clinical isolates. The resulting Southern blot analysis demonstrated a marked DNA polymorphism of multiple vspA-related fragm ents among the isolates. An oligonucleotide representing a conserved 5 '-region common to all known vsp genes, was found to hybridize to mult iple M. agalactiae genomic fragments while the other three oligonucleo tides, representing distinct repetitive structures within the coding r egion of three known vsp genes (vspA, vspE, and vspF), failed to react . These results argue for the possible existence of a gene family in M . agalactiae analogous to the vsp system of M. bovis but comprised of diverse genes.