title: Genome comparison and phylogenetic analysis of Orientia tsutsugamushi strains.
abstract: Orientia tsutsugamushi (OT) is an obligate intracellular bacterium belonging to the family Rickettsiaceae and is the causative agent of scrub typhus, or Tsutsugamushi disease. The complete genome sequences of two OT strains (Boryong and Ikeda) have recently been determined. In the present study, we performed a fine genome sequence comparison of these strains. Our results indicate that although the core gene set of the family Rickettsiaceae is highly conserved between the two strains, a common set of repetitive sequences have been explosively amplified in both genomes. These amplified repetitive sequences have induced extensive genome shuffling and duplications and deletions of many genes. On the basis of the results of the genome sequence comparison, we selected 11 housekeeping genes and carried out multilocus sequence analysis of OT strains using the nucleotide sequences of these genes. This analysis revealed for the first time the phylogenetic relationships of representative OT strains. Furthermore, the results suggest the presence of an OT lineage with higher potential for virulence, which may explain the clinical and epidemiological differences between 'classic' and 'new' types of Tsutsugamushi disease in Japan.
authors.affiliation: Division of Microbiology, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kiyotake, Miyazaki 899-1692, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Nakayama
authors.forename: Ken
authors.initials: K
authors.lastname: Kurokawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Fukuhara
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Urakami
authors.forename: Seigo
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Kazuko
authors.initials: K
authors.lastname: Yamazaki
authors.forename: Yoshitoshi
authors.initials: Y
authors.lastname: Ogura
authors.forename: Tadasuke
authors.initials: T
authors.lastname: Ooka
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hayashi
mesh_terms: D001483:Base Sequence; D020451:Contig Mapping; D004269:DNA, Bacterial / Q000235:genetics*; D016680:Genome, Bacterial; D012285:Orientia tsutsugamushi / Q000145:classification / Q000235:genetics; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012287:Rickettsiaceae / Q000235:genetics*; D012612:Scrub Typhus / Q000382:microbiology; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial