Extremely low genomic diversity of Rickettsia japonica distributed in Japan

Arzuba Akter, Tadasuke Ooka, Yasuhiro Gotoh, Seigo Yamamoto, Hiromi Fujita, Fumio Terasoma, Kouji Kida, Masakatsu Taira, Fumiko Nakadouzono, Mutsuyo Gokuden, Manabu Hirano, Mamoru Miyashiro, Kouichi Inari, Yukie Shimazu, Kenji Tabara, Atsushi Toyoda, Dai Yoshimura, Takehiko Itoh, Tomokazu Kitano, Mitsuhiko P. SatoKeisuke Katsura, Shakhinur Islam Mondal, Yoshitoshi Ogura, Shuji Ando, Tetsuya Hayashi

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


Rickettsiae are obligate intracellular bacteria that have small genomes as a result of reductive evolution. Many Rickettsia species of the spotted fever group (SFG) cause tick-borne diseases known as "spotted fevers". The life cycle of SFG rickettsiae is closely associated with that of the tick, which is generally thought to act as a bacterial vector and reservoir that maintains the bacterium through transstadial and transovarial transmission. Each SFG member is thought to have adapted to a specific tick species, thus restricting the bacterial distribution to a relatively limited geographic region. These unique features of SFG rickettsiae allow investigation of how the genomes of such biologically and ecologically specialized bacteria evolve after genome reduction and the types of population structures that are generated. Here, we performed a nationwide, high-resolution phylogenetic analysis of Rickettsia japonica, an etiological agent of Japanese spotted fever that is distributed in Japan and Korea. The comparison of complete or nearly complete sequences obtained from 31 R. japonica strains isolated from various sources in Japan over the past 30 years demonstrated an extremely low level of genomic diversity. In particular, only 34 single nucleotide polymorphisms were identified among the 27 strains of themajor lineage containing all clinical isolates and tick isolates from the three tick species. Our data provide novel insights into the biology and genome evolution of R. japonica, including the possibilities of recent clonal expansion and a long generation time in nature due to the long dormant phase associated with tick life cycles.

Original languageEnglish
Pages (from-to)124-133
Number of pages10
JournalGenome biology and evolution
Issue number1
Publication statusPublished - Jan 1 2017

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Genetics


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