The lifestyle of the segmented filamentous bacterium: A non-culturable gut-associated immunostimulating microbe inferred by whole-genome sequencing

Tomomi Kuwahara, Yositoshi Ogura, Kenshiro Oshima, Ken Kurokawa, Tadasuke Ooka, Hideki Hirakawa, Takehiko Itoh, Haruyuki Nakayama-Imaohji, Minoru Ichimura, Kikuji Itoh, Chieko Ishifune, Yoichi Maekawa, Koji Yasutomo, Masahira Hattori, Tetsuya Hayashi

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60 Citations (Scopus)


Numerous microbes inhabit the mammalian intestinal track and strongly impact host physiology; however, our understanding of this ecosystem remains limited owing to the high complexity of the microbial community and the presence of numerous non-culturable microbes. Segmented filamentous bacteria (SFBs), which are clostridia-related Gram-positive bacteria, are among such non-culturable populations and are well known for their unique morphology and tight attachment to intestinal epithelial cells. Recent studies have revealed that SFBs play crucial roles in the post-natal maturation of gut immune function, especially the induction of Th17 lymphocytes. Here, we report the complete genome sequence of mouse SFBs. The genome, which comprises a single circular chromosome of 1 620 005 bp, lacks genes for the biosynthesis of almost all amino acids, vitamins/cofactors and nucleotides, but contains a full set of genes for sporulation/germination and, unexpectedly, for chemotaxis/flagella- based motility. These findings suggest a triphasic lifestyle of the SFB, which comprises two types of vegetative (swimming and epicellular parasitic) phases and a dormant (spore) phase. Furthermore, SFBs encode four types of flagellin, three of which are recognized by Toll-like receptor 5 and could elicit the innate immune response. Our results reveal the non-culturability, lifestyle and immunostimulation mechanisms of SFBs and provide a genetic basis for the future development of the SFB cultivation and gene-manipulation techniques.

Original languageEnglish
Pages (from-to)291-303
Number of pages13
JournalDNA Research
Issue number4
Publication statusPublished - Aug 1 2011
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Genetics

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