title: Just one cross appears capable of dramatically altering the population biology of a eukaryotic pathogen like Toxoplasma gondii.
abstract: Toxoplasma gondii, an obligate intracellular protozoan of the phylum Apicomplexa, is estimated to infect over a billion people worldwide as well as a great many other mammalian and avian hosts. Despite this ubiquity, the vast majority of human infections in Europe and North America are thought to be due to only three genotypes. Using a genome-wide analysis of single-nucleotide polymorphisms, we have constructed a genealogy for these three lines. The data indicate that types I and III are second- and first-generation offspring, respectively, of a cross between a type II strain and one of two ancestral strains. An extant T. gondii strain (P89) appears to be the modern descendant of the non-type II parent of type III, making the full genealogy of the type III clonotype known. The simplicity of this family tree demonstrates that even a single cross can lead to the emergence and dominance of a new clonal genotype that completely alters the population biology of a sexual pathogen.
authors.affiliation: *Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305.
authors.forename: Jon P
authors.initials: JP
authors.lastname: Boyle
authors.affiliation: *Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305.
authors.forename: Badri
authors.initials: B
authors.lastname: Rajasekar
authors.affiliation: *Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305.
authors.forename: Jeroen P J
authors.initials: JPJ
authors.lastname: Saeij
authors.affiliation: Department of Pathology, Cambridge University, Cambridge CB2 1QP, United Kingdom.
authors.forename: James W
authors.initials: JW
authors.lastname: Ajioka
authors.affiliation: Wellcome Trust Sanger Institute, Hinxton CB10 1SA, United Kingdom.
authors.forename: Matthew
authors.initials: M
authors.lastname: Berriman
authors.affiliation: Institute for Genomic Research, Rockville, MD 20850.
authors.forename: Ian
authors.initials: I
authors.lastname: Paulsen
authors.affiliation: Department of Biology and Penn Genomics Institute, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: David S
authors.initials: DS
authors.lastname: Roos
authors.affiliation: Department of Molecular Microbiology, Center for Infectious Diseases, Washington University School of Medicine, St. Louis, MO 63110; and.
authors.forename: L David
authors.initials: LD
authors.lastname: Sibley
authors.affiliation: **Department of Veterinary Molecular Biology, Montana State University, Bozeman, MT 59717.
authors.forename: Michael W
authors.initials: MW
authors.lastname: White
authors.affiliation: *Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305; john.boothroyd@stanford.edu.
authors.forename: John C
authors.initials: JC
authors.lastname: Boothroyd
mesh_terms: D000818:Animals; D002875:Chromosomes / Q000235:genetics; D003433:Crosses, Genetic; D005260:Female; D018503:Genome, Protozoan / Q000235:genetics; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D014122:Toxoplasma / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology*