title: Pan-genome of the dominant human gut-associated archaeon, Methanobrevibacter smithii, studied in twins.
abstract: The human gut microbiota harbors three main groups of H(2)-consuming microbes: methanogens including the dominant archaeon, Methanobrevibacter smithii, a polyphyletic group of acetogens, and sulfate-reducing bacteria. Defining their roles in the gut is important for understanding how hydrogen metabolism affects the efficiency of fermentation of dietary components. We quantified methanogens in fecal samples from 40 healthy adult female monozygotic (MZ) and 28 dizygotic (DZ) twin pairs, analyzed bacterial 16S rRNA datasets generated from their fecal samples to identify taxa that co-occur with methanogens, sequenced the genomes of 20 M. smithii strains isolated from families of MZ and DZ twins, and performed RNA-Seq of a subset of strains to identify their responses to varied formate concentrations. The concordance rate for methanogen carriage was significantly higher for MZ versus DZ twin pairs. Co-occurrence analysis revealed 22 bacterial species-level taxa positively correlated with methanogens: all but two were members of the Clostridiales, with several being, or related to, known hydrogen-producing and -consuming bacteria. The M. smithii pan-genome contains 987 genes conserved in all strains, and 1,860 variably represented genes. Strains from MZ and DZ twin pairs had a similar degree of shared genes and SNPs, and were significantly more similar than strains isolated from mothers or members of other families. The 101 adhesin-like proteins (ALPs) in the pan-genome (45 ± 6 per strain) exhibit strain-specific differences in expression and responsiveness to formate. We hypothesize that M. smithii strains use their different repertoires of ALPs to create diversity in their metabolic niches, by allowing them to establish syntrophic relationships with bacterial partners with differing metabolic capabilities and patterns of co-occurrence.
authors.affiliation: Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, MO 63108, USA.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Hansen
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Lozupone
authors.forename: Federico E
authors.initials: FE
authors.lastname: Rey
authors.forename: Meng
authors.initials: M
authors.lastname: Wu
authors.forename: Janaki L
authors.initials: JL
authors.lastname: Guruge
authors.forename: Aneesha
authors.initials: A
authors.lastname: Narra
authors.forename: Jonathan
authors.initials: J
authors.lastname: Goodfellow
authors.forename: Jesse R
authors.initials: JR
authors.lastname: Zaneveld
authors.forename: Daniel T
authors.initials: DT
authors.lastname: McDonald
authors.forename: Julia A
authors.initials: JA
authors.lastname: Goodrich
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Heath
authors.forename: Rob
authors.initials: R
authors.lastname: Knight
authors.forename: Jeffrey I
authors.initials: JI
authors.lastname: Gordon
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics*; D000328:Adult; D001483:Base Sequence; D005260:Female; D005561:Formates / Q000032:analysis; D041981:Gastrointestinal Tract / Q000382:microbiology*; D020745:Genome, Archaeal; D006801:Humans; D056186:Metagenomics; D041581:Methanobrevibacter / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D014427:Twins
chemical_list: D018829:Adhesins, Bacterial; D005561:Formates; D012336:RNA, Ribosomal, 16S; C030544:formic acid