title: Intracellular pathogens go extreme: genome evolution in the Rickettsiales.
abstract: The Rickettsiales, a genetically diverse group of the alpha-Proteobacteria, include major mammalian pathogens, such as the agents of epidemic typhus, scrub typhus, ehrlichioses and heartwater disease. Sequenced genomes of this bacterial order have provided exciting insights into reductive genome evolution, antigenic variation and host cell manipulation. Recent results suggest that human pathogens emerged relatively late in the evolution of the Rickettsiales. Surprisingly, there is no association between pathogenicity and the acquisition of novel virulence genes. Here, we explore the genomic differences between members of the Rickettsiales and ask what are the changes that enable infectious agents to emerge from seemingly harmless bacteria.
authors.affiliation: Department of Molecular Evolution, Evolutionary Biology Center, Uppsala University, Norbyvägen 18C, S-752 36 Uppsala, Sweden.
authors.forename: Alistair C
authors.initials: AC
authors.lastname: Darby
authors.forename: Nam-Huyk
authors.initials: NH
authors.lastname: Cho
authors.forename: Hans-Henrik
authors.initials: HH
authors.lastname: Fuxelius
authors.forename: Joakim
authors.initials: J
authors.lastname: Westberg
authors.forename: Siv G E
authors.initials: SG
authors.lastname: Andersson
mesh_terms: D020561:Alphaproteobacteria / Q000235:genetics* / Q000472:pathogenicity*; D001426:Bacterial Proteins; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D006801:Humans; D008957:Models, Genetic; D012285:Orientia tsutsugamushi / Q000235:genetics; D012281:Rickettsia / Q000235:genetics; D014774:Virulence; D020577:Wolbachia / Q000235:genetics