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Occurrence, plasticity, and evolution of the vpma gene family, a genetic system devoted to high-frequency surface

Laurent-Xavier Nouvel1, Marc Marenda, Pascal Sirand-Pugnet

  • 1Université de Toulouse, ENVT, UMR 1225, F-31076 Toulouse, France.

Journal of Bacteriology
|April 21, 2009
PubMed

Insights

Mycoplasma agalactiae surface protein diversity is significantly higher in field strains due to expanded variable surface lipoproteins (Vpma) gene repertoires and chromosomal rearrangements. This genetic plasticity impacts pathogen evolution and epidemiology.

Area of Science:

  • Microbiology
  • Genomics
  • Pathogen Evolution

Background:

  • Mycoplasma agalactiae causes disease in small ruminants.
  • Surface protein variation (Vpma phase variation) is key to M. agalactiae pathogenicity.
  • The type strain PG2 has a single cluster of six vpma genes.

Purpose of the Study:

  • To analyze the vpma gene repertoire in a field strain (5632) of Mycoplasma agalactiae.
  • To understand the genetic mechanisms generating surface diversity in M. agalactiae.
  • To assess the evolutionary and epidemiological implications of vpma gene variation.

Main Methods:

  • Whole-genome analysis of the field strain 5632.
  • Identification and characterization of vpma gene loci.
  • Proteomic analysis to determine Vpma expression.
  • Investigation of insertion sequences and recombination events.

Main Results:

  • Field strain 5632 possesses an expanded repertoire of 23 vpma genes across two distant loci.
  • Loci contain duplicated genes, with Vpma chimerism suggesting homologous recombination.
  • At least 13 Vpmas are expressed, leading to greater surface combination possibilities than the type strain.
  • Insertion sequences are implicated in vpma locus duplication.

Conclusions:

  • Field strains of M. agalactiae exhibit significantly greater surface protein diversity than previously understood.
  • Chromosomal rearrangements and gene duplications drive this enhanced variability.
  • Mobile genetic elements play a crucial role in shaping the genomes of wall-less pathogens like mycoplasmas.

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