Episymbiotic Saccharibacteria suppresses gingival inflammation and bone loss in mice through host bacterial modulation

Cell Host Microbe. 2021 Nov 10;29(11):1649-1662.e7. doi: 10.1016/j.chom.2021.09.009. Epub 2021 Oct 11.

Abstract

Saccharibacteria (TM7) are obligate epibionts living on the surface of their host bacteria and are strongly correlated with dysbiotic microbiomes during periodontitis and other inflammatory diseases, suggesting they are putative pathogens. However, due to the recalcitrance of TM7 cultivation, causal research to investigate their role in inflammatory diseases is lacking. Here, we isolated multiple TM7 species on their host bacteria from periodontitis patients. These TM7 species reduce inflammation and consequential bone loss by modulating host bacterial pathogenicity in a mouse ligature-induced periodontitis model. Two host bacterial functions involved in collagen binding and utilization of eukaryotic sialic acid are required for inducing bone loss and are altered by TM7 association. This TM7-mediated downregulation of host bacterial pathogenicity is shown for multiple TM7/host bacteria pairs, suggesting that, in contrast to their suspected pathogenic role, TM7 could protect mammalian hosts from inflammatory damage induced by their host bacteria.

Keywords: Actinobacteria; Actinomyces; Saccharibacteria; TM7; bacterial symbiosis; candidate phyla radiation; human microbiome; human oral microbiome; inflammatory disease; periodontitis.

MeSH terms

  • Actinobacteria / genetics
  • Actinobacteria / isolation & purification
  • Actinobacteria / pathogenicity*
  • Actinobacteria / physiology
  • Actinomyces / genetics
  • Actinomyces / isolation & purification
  • Actinomyces / pathogenicity
  • Actinomyces / physiology
  • Alveolar Bone Loss / microbiology*
  • Alveolar Bone Loss / prevention & control
  • Animals
  • Bacteria / classification
  • Bacteria / isolation & purification
  • Bacteria / pathogenicity
  • Bacterial Infections / microbiology
  • Bacterial Infections / prevention & control
  • Bacterial Physiological Phenomena*
  • Collagen / metabolism
  • Dental Plaque / microbiology
  • Down-Regulation
  • Genes, Bacterial
  • Gingivitis / microbiology*
  • Gingivitis / prevention & control
  • Humans
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Microbiota
  • N-Acetylneuraminic Acid / metabolism
  • Periodontitis / microbiology*
  • Periodontitis / prevention & control
  • Propionibacteriaceae / genetics
  • Propionibacteriaceae / isolation & purification
  • Propionibacteriaceae / pathogenicity
  • Propionibacteriaceae / physiology
  • Symbiosis*
  • Virulence

Substances

  • Collagen
  • N-Acetylneuraminic Acid