title: Global genetic population structure of Bacillus anthracis.
abstract: Anthrax, caused by the bacterium Bacillus anthracis, is a disease of historical and current importance that is found throughout the world. The basis of its historical transmission is anecdotal and its true global population structure has remained largely cryptic. Seven diverse B. anthracis strains were whole-genome sequenced to identify rare single nucleotide polymorphisms (SNPs), followed by phylogenetic reconstruction of these characters onto an evolutionary model. This analysis identified SNPs that define the major clonal lineages within the species. These SNPs, in concert with 15 variable number tandem repeat (VNTR) markers, were used to subtype a collection of 1,033 B. anthracis isolates from 42 countries to create an extensive genotype data set. These analyses subdivided the isolates into three previously recognized major lineages (A, B, and C), with further subdivision into 12 clonal sub-lineages or sub-groups and, finally, 221 unique MLVA15 genotypes. This rare genomic variation was used to document the evolutionary progression of B. anthracis and to establish global patterns of diversity. Isolates in the A lineage are widely dispersed globally, whereas the B and C lineages occur on more restricted spatial scales. Molecular clock models based upon genome-wide synonymous substitutions indicate there was a massive radiation of the A lineage that occurred in the mid-Holocene (3,064-6,127 ybp). On more recent temporal scales, the global population structure of B. anthracis reflects colonial-era importation of specific genotypes from the Old World into the New World, as well as the repeated industrial importation of diverse genotypes into developed countries via spore-contaminated animal products. These findings indicate humans have played an important role in the evolution of anthrax by increasing the proliferation and dispersal of this now global disease. Finally, the value of global genotypic analysis for investigating bioterrorist-mediated outbreaks of anthrax is demonstrated.
authors.affiliation: Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, United States of America.
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Van Ert
authors.forename: W Ryan
authors.initials: WR
authors.lastname: Easterday
authors.forename: Lynn Y
authors.initials: LY
authors.lastname: Huynh
authors.forename: Richard T
authors.initials: RT
authors.lastname: Okinaka
authors.forename: Martin E
authors.initials: ME
authors.lastname: Hugh-Jones
authors.forename: Jacques
authors.initials: J
authors.lastname: Ravel
authors.forename: Shaylan R
authors.initials: SR
authors.lastname: Zanecki
authors.forename: Talima
authors.initials: T
authors.lastname: Pearson
authors.forename: Tatum S
authors.initials: TS
authors.lastname: Simonson
authors.forename: Jana M
authors.initials: JM
authors.lastname: U'Ren
authors.forename: Sergey M
authors.initials: SM
authors.lastname: Kachur
authors.forename: Rebecca R
authors.initials: RR
authors.lastname: Leadem-Dougherty
authors.forename: Shane D
authors.initials: SD
authors.lastname: Rhoton
authors.forename: Guenevier
authors.initials: G
authors.lastname: Zinser
authors.forename: Jason
authors.initials: J
authors.lastname: Farlow
authors.forename: Pamala R
authors.initials: PR
authors.lastname: Coker
authors.forename: Kimothy L
authors.initials: KL
authors.lastname: Smith
authors.forename: Bingxiang
authors.initials: B
authors.lastname: Wang
authors.forename: Leo J
authors.initials: LJ
authors.lastname: Kenefic
authors.forename: Claire M
authors.initials: CM
authors.lastname: Fraser-Liggett
authors.forename: David M
authors.initials: DM
authors.lastname: Wagner
authors.forename: Paul
authors.initials: P
authors.lastname: Keim
mesh_terms: D001408:Bacillus anthracis / Q000235:genetics*; D016000:Cluster Analysis; D005798:Genes, Bacterial; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide