Fig. 3

Putative functions of the MAGs in the anaerobic digestion food web (a). The asterisk (MAG-R9) indicates a potential function that merely proposed in literature (see text for details). Wood-Ljungdahl pathway genes in MAGs of syntrophic and putatively syntrophic bacteria as well as the corresponding energy-conserving mechanisms (b). Hyd, [FeFe] hydrogenase group A3; Hdr, heterodisulfide reductase; NiFe H2ase, energy-conserving group 1a [NiFe] hydrogenase; Rnf, Na⁺/H⁺ translocating ferredoxin:NAD⁺ oxidoreductase; Q, quinone; ETF, electron transfer flavoprotein; ETF-Q OR, electron transfer flavoprotein/quinone oxidoreductase; FDH, formate dehydrogenase; Ftr, formate transporter; EM, electron mediator; CM, cytoplasmic membrane; THF, tetrahydrofolate. Genes involved in the Wood-Ljungdahl pathway are acetate kinase (1), phosphotransacetylase (2), acetyl-CoA synthase complex including corrinoid protein (CoFeSP) (3), carbon monoxide dehydrogenase (4), methyltransferase (5), methylene-THF reductase (6), methylene-THF dehydrogenase (7), methenyl-THF cyclohydrolase (8), formyl-THF synthethase (9), and formate dehydrogenase (10)