title: The population structure of Mycobacterium bovis in Great Britain: clonal expansion.
abstract: We have analyzed 11,500 isolates of Mycobacterium bovis (the cause of tuberculosis in cattle and other mammals) isolated in Great Britain (England, Wales and Scotland)] and characterized by spoligotype. Genetic exchange between cells is rare or absent in strains of the Mycobacterium tuberculosis complex so that, by using spoligotypes, it is possible to recognize "clones" with a recent common ancestor. The distribution of variable numbers of tandem repeats types in the most common clone in the data set is incompatible with random mutation and drift. The most plausible explanation is a series of "clonal expansions," and this interpretation is supported by the geographical distribution of different genotypes. We suggest that the clonal expansion of a genotype is caused either by the spread of a favorable mutation, together with all other genes present in the ancestral cell in which the mutation occurred, or by the invasion of a novel geographical region by a limited number of genotypes. A similar pattern is observed in M. tuberculosis (the main cause of tuberculosis in humans). The significance of clonal expansion in other bacteria that have recombination is discussed.
authors.affiliation: Centre for the Study of Evolution, University of Sussex, Falmer, Brighton BN1 9QL, United Kingdom.
authors.forename: Noel H
authors.initials: NH
authors.lastname: Smith
authors.forename: James
authors.initials: J
authors.lastname: Dale
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Inwald
authors.forename: Si
authors.initials: S
authors.lastname: Palmer
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Gordon
authors.forename: R Glyn
authors.initials: RG
authors.lastname: Hewinson
authors.forename: John Maynard
authors.initials: JM
authors.lastname: Smith
mesh_terms: D018407:Bacterial Physiological Phenomena; D004269:DNA, Bacterial; D014644:Genetic Variation; D005838:Genotype; D018598:Minisatellite Repeats; D008957:Models, Genetic; D009154:Mutation; D009163:Mycobacterium bovis / Q000235:genetics*; D009169:Mycobacterium tuberculosis / Q000235:genetics; D010802:Phylogeny; D006113:United Kingdom
chemical_list: D004269:DNA, Bacterial