The Lifestyle of the Segmented Filamentous Bacterium: A Non-Culturable Gut-Associated Immunostimulating Microbe Inferred by Whole-Genome Sequencing

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 (SFB...

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Published in:	DNA research Vol. 18; no. 4; pp. 291 - 303
Main Authors:	TOMOMI, Kuwahara, YOSITOSHI, Ogura, CHIEKO, Ishifune, YOICHI, Maekawa, KOJI, Yasutomo, MASAHIRA, Hattori, TETSUYA, Hayashi, KENSHIRO, Oshima, KEN, Kurokawa, TADASUKE, Ooka, HIDEKI, Hirakawa, TAKEHIKO, Itoh, HARUYUKI, Nakayama-Imaohji, MINORU, Ichimura, KIKUJI, Itoh
Format:	Journal Article
Language:	English
Published:	Oxford Oxford University Press 01-08-2011
Subjects:	Animals Bacteria - genetics Bacteria - immunology Bacteria - metabolism Bacteria - ultrastructure Biological and medical sciences Biosynthetic Pathways - genetics Chemotaxis Chromosomes, Bacterial - genetics Flagella - metabolism Flagellin - immunology Flagellin - metabolism Fundamental and applied biological sciences. Psychology Gene Order Genes. Genome Genetics of eukaryotes. Biological and molecular evolution Genome, Bacterial - genetics Humans Intestines - microbiology Male Mice Mice, Inbred BALB C Molecular and cellular biology Molecular genetics Phylogeny Sequence Analysis, DNA Spores flagella segmented filamentous bacterium Digestive system non-culturable bacteria Gut Bacteria Genome Sequencing Life style
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Summary:	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.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 These authors contributed equally to this study. Edited by Katsumi Isono
ISSN:	1340-2838 1756-1663
DOI:	10.1093/dnares/dsr022