title: Comparative genomics of three strains of Ehrlichia ruminantium: a review.
abstract: The tick-borne Rickettsiale Ehrlichia ruminantium (E. ruminantium) is the causative agent of heartwater in Africa and the Caribbean. Heartwater, responsible for major losses on livestock in Africa represents also a threat for the American mainland. Three complete genomes corresponding to two different groups of differing phenotypes, Gardel and Welgevonden, have been recently described. One genome (Erga) represents the Gardel group from Guadeloupe Island and two genomes (Erwo and Erwe) belong to the Welgevonden group. Erwo, isolated in South Africa, is the parental strain of Erwe, which was maintained for 18 years in Guadeloupe under different culture conditions than Erwo. The three strains display genomes of differing sizes with 1,499,920 bp, 1,512,977 bp, and 1,516,355 bp for Erga, Erwe, and Erwo, respectively. Gene sequences and order are highly conserved between the three strains, although several gene truncations could be pinpointed, most of them occurring within three regions of accumulated differences (RAD). E. ruminantium displays a strong leading/lagging compositional bias inducing a strand-specific codon usage. Finally, a striking feature of E. ruminantium is the presence of long intergenic regions containing tandem repeats. These repeats are at the origin of an active process, specific to E. ruminantium, of genome expansion/contraction based on the addition or removal of tandem units.
authors.affiliation: CIRAD, Emvt Department, TA30/G, Campus International de Baillarguet, 34398 Montpellier Cedex 5, France. roger.frutos@cirad.fr
authors.forename: Roger
authors.initials: R
authors.lastname: Frutos
authors.forename: Alain
authors.initials: A
authors.lastname: Viari
authors.forename: Conchita
authors.initials: C
authors.lastname: Ferraz
authors.forename: Albert
authors.initials: A
authors.lastname: Bensaid
authors.forename: Anne
authors.initials: A
authors.lastname: Morgat
authors.forename: Frederic
authors.initials: F
authors.lastname: Boyer
authors.forename: Eric
authors.initials: E
authors.lastname: Coissac
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vachiéry
authors.forename: Jacques
authors.initials: J
authors.lastname: Demaille
authors.forename: Dominique
authors.initials: D
authors.lastname: Martinez
mesh_terms: D000818:Animals; D017124:Conserved Sequence; D016995:Ehrlichia ruminantium / Q000235:genetics*; D019143:Evolution, Molecular; D016680:Genome, Bacterial; D008969:Molecular Sequence Data; D008970:Molecular Weight; D013045:Species Specificity; D020080:Tandem Repeat Sequences / Q000235:genetics*