Complete genome sequencing of Anaplasma marginale reveals that the surface is skewed to two superfamilies of outer membrane proteins

Proc Natl Acad Sci U S A. 2005 Jan 18;102(3):844-9. doi: 10.1073/pnas.0406656102. Epub 2004 Dec 23.


The rickettsia Anaplasma marginale is the most prevalent tick-borne livestock pathogen worldwide and is a severe constraint to animal health. A. marginale establishes lifelong persistence in infected ruminants and these animals serve as a reservoir for ticks to acquire and transmit the pathogen. Within the mammalian host, A. marginale generates antigenic variants by changing a surface coat composed of numerous proteins. By sequencing and annotating the complete 1,197,687-bp genome of the St. Maries strain of A. marginale, we show that this surface coat is dominated by two families containing immunodominant proteins: the msp2 superfamily and the msp1 superfamily. Of the 949 annotated coding sequences, just 62 are predicted to be outer membrane proteins, and of these, 49 belong to one of these two superfamilies. The genome contains unusual functional pseudogenes that belong to the msp2 superfamily and play an integral role in surface coat antigenic variation, and are thus distinctly different from pseudogenes described as byproducts of reductive evolution in other Rickettsiales.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anaplasma marginale / genetics*
  • Antigenic Variation
  • Antigens, Bacterial / genetics*
  • Bacterial Outer Membrane Proteins / genetics*
  • Base Sequence
  • Immunodominant Epitopes
  • Molecular Sequence Data
  • Multigene Family
  • Pseudogenes
  • Sequence Analysis


  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Immunodominant Epitopes
  • major surface protein 1a, Anaplasma
  • major surface protein 1b, Anaplasma
  • msp2 protein, Anaplasma marginale

Associated data

  • GENBANK/CP000030