Syntrophy

Edge evidence

• Syntrophy requires partner interaction methanogenic product consumption

  Syntrophic metabolism depends on a partner that consumes products.

  • DOI:10.1038/nrmicro2166 metabolic abilities of their syntrophic partner Supports partner dependence in syntrophic communities.
• syntrophic product formation transfers electrons via molecular hydrogen METPO:2007600

  Hydrogen can carry reducing equivalents between syntrophic partners.

  • DOI:10.1038/nrmicro2166 Hydrogen and formate are key components Supports hydrogen as a key interspecies electron-transfer carrier.
• syntrophic product formation transfers electrons via formate METPO:2007600

  Formate can carry reducing equivalents between syntrophic partners.

  • DOI:10.1038/nrmicro2166 transfer of hydrogen and formate Supports formate-mediated interspecies electron transfer.
• methanogenic product consumption consumes molecular hydrogen biolink:consumes

  Methanogens keep hydrogen concentrations low enough for syntrophic metabolism.

  • DOI:10.1038/nrmicro2166 low hydrogen concentrations, which are created by the methanogen Supports product removal by methanogens as a thermodynamic driver.
• methanogenic product consumption creates low hydrogen condition biolink:produces

  Hydrogen consumption creates the product-removal condition needed by the syntroph.

  • DOI:10.1038/nrmicro2166 live at the limits of what is thermodynamically possible Supports the thermodynamic constraint that product removal relieves.
• molecular hydrogen participates in methanogenesis biolink:participates_in

  Hydrogen can feed methanogenesis in syntrophic communities.

  • DOI:10.1038/nrmicro2166 syntrophic methanogenic communities Supports hydrogen-linked electron flow into methanogenic partners.
• low hydrogen partial pressure enables interspecies hydrogen transfer RO:0002327

  H2-mediated transfer is thermodynamically feasible only at extremely low H2 partial pressure.

  • DOI:10.3390/fermentation9050467 H2-mediated transfer thermodynamically feasible only when H2 < 10^-4 atm.
• interspecies hydrogen transfer mediates Syntrophy

  Interspecies hydrogen transfer is a core mechanistic sub-process of syntrophy.

  • DOI:10.3390/fermentation9050467 H2-mediated MIET (IHT) is a main interspecies electron transfer mode relevant to syntrophy.
• interspecies formate transfer mediates Syntrophy

  Interspecies formate transfer is a core mechanistic sub-process of syntrophy.

  • DOI:10.1093/femsre/fuab057 Interspecies formate transfer is one of three IET mechanisms in syntrophic propionate oxidation.
• formate dehydrogenase complex mediates interspecies formate transfer

  Formate dehydrogenases provide the enzymatic basis for formate production/consumption in syntrophy.

  • DOI:10.1186/s40168-020-00885-y Formate dehydrogenases and formate transporters expressed by FA-degrading syntrophic species.
• hydrogenase complex mediates interspecies hydrogen transfer

  Hydrogenases provide the enzymatic basis for H2 production/consumption in syntrophy.

  • DOI:10.1038/s41396-023-01504-y Hydrogen-mediated transfer supported by expression of hydrogenases in syntrophic communities.
• direct interspecies electron transfer bypasses hydrogen pressure inhibition

  DIET can overcome inhibition by hydrogen pressure, enabling syntrophy without soluble carriers.

  • DOI:10.3390/fermentation9100884 DIET can overcome the inhibition of hydrogen pressure and formate concentration.
• conductive pili (e-pili) mediates direct interspecies electron transfer

  Conductive pili (e-pili) are a canonical DIET conduit.

  • DOI:10.1134/S0026261720020101 DIET occurs via conductive pili (e-pili).
• multiheme c-type cytochromes mediates direct interspecies electron transfer

  Outer-surface multiheme c-type cytochromes are a core DIET redox conduit.

  • DOI:10.3390/life14050591 DIET operates via outer-surface c-type cytochromes.