Nomenclature of MAGs in this study

Based on the data presented above, we propose the following taxonomic epithets “Ca. Methanohydrogenotrophilum pristinum” (JZ bin_68, JZ bin_38), “Ca. Geoarchaeum hydrogenovorans” (ZMQR bin_18, GMQP bin_37), “Ca. Methanomethylovorus thermophilus” (JZ-2 bin_200, JZ-3 bin_106, JZ-3 bin_107, DRTY-6 bin_144), “Ca. Methanomethylarchaeum antiquum” (GMQP bin_44), “Ca. Methanourarchaeum thermotelluricum” (JZ-1 bin_103), “Ca. Hadesarchaeum tengchongensis” (JZ-2 bin_199), “Ca. Methanomixtatrophicum sinensis” (JZ-2 bin_168), “Ca. Methanoproducendum senex” (GMQP bin_32), and “Ca. Methylarchaeum tengchongensis” (JZ-2 bin_220). The etymology and descriptions are provided below. The proposed taxonomy of these organisms is summarized in Supplementary Table ³.

“Methanohydrogenotrophicum” (Me.tha.no.hy.dro.gen’o.tro.phi.cum) M. L. n. methanum methane; Gr. n. hydoor, water; Gr. n. gennao, to create; M.L. hydrogenum, hydrogen, that which produces water; N.L. neut. adj. trophicum (from Gr. neut. adj. trophikon) nursing, tending or feeding; N.L. neut. n. hydrogenotrophicum hydrogenotroph; N.L. neut. n. Methanohydrogenotrophicum, methane (-producing) hydrogenotroph. The type species is “Ca. Methanohydrogenotrophicum pristinum”. “Ca. Methanohydrogenotrophicum pristinum” (pris.ti’num) L. masc. adj. pristinum, ancient, venerable. The type material is the metagenomic bin JZ bin_66 (Ga0263245). “Methanogeoarchaeum” (Me.tha.no.ge’o.ar.chae.um) M. L. n. methanum methane; Gr. n. geo Earth; Gr. adj. archeo ancient, also referring to Archaea; Methanogeoarchaeum, methane (-producing) terrestrial archaeon. The type species is “Ca. Methanogeoarchaeum hydrogenovorans”. “Ca. Methanogeoarchaeum hydrogenovorans” (hy.dro.gen.o.vo’rans) M.L. hydrogenum, hydrogen, that which produces water; L. masc. vorus, devouring; L. part. hydrogenovorans, hydrogen-devouring. The type material is the metagenomic bin ZMQR bin_18 (Ga0263256). Phylogenomic analyses support the proposal for a new family inclusive of both “Ca. Methanohydrogenotrophicum pristinum” and “Ca. Methanogeoarchaeum hydrogenovorans”, Methanohydrogenotrophicaceae (Me.tha.no.hy.dro.gen’o.tro.phi.ca’ce.ae) N.L. n. Methanohydrogenotrophicum type genus of the family; L. suff. -aceae ending to denote a family; N.L. fem. pl. n. Methanohydrogenotrophicaceae the family of the genus Methanohydrogenotrophicum.

“Methanomethylovorus” (Me.tha.no.me.thy’lo.vo.rus) M. L. n. methanum methane; methylo, methyl, referring to the methylotrophic methane-producing metabolism; L. masc. vorus, devouring; L. part. Methanomethylovorus, methyl group-devouring methanogen. The type species is “Ca. Methanomethylovorus thermophilus”. “Ca. Methanomethylovorus thermophilus” (ther.mo’phi.lus). Gr. n. therme heat; Gr. adj. philos friendly, loving; N.L. masc. adj. thermophilus heat-loving. The type material is the metagenomic bin JZ-2 bin_200 (Ga0263249). “Methanomethyloarchaeum” (Me.tha.no.me.thy’lo.ar.chae.um) M. L. n. methanum methane; methylo, methyl, referring to the methylotrophic methane-producing metabolism; Gr. adj. archeo ancient, also referring to Archaea; Methanomethyloarchaeum, methylotrophic methanogen belonging to the Archaea. The type species is “Ca. Methanomethyloarchaeum antiquum”. “Ca. Methanomethyloarchaeum antiquum” (an.ti’.quum) M. L. adj. ancient, referring to the deep-branching position in the Archaea. The type material is the metagenomic bin GMQP bin_44 (Ga0263253). Similarly, two new orders are proposed correspondingly, Methanomethylovorales (Me.tha.no.me.thy’lo.vo.ra’les) N.L. n. Methanomethylovorus type genus of the order, and Methanomethyloarchaeales (Me.tha.no.me.thy’lo.ar.chae’ales) N.L. n. Methanomethyloarchaeum type genus of the order; L. suff. -ales ending to denote an order.

“Hadesarchaeum” (Ha’des.ar.chae.um) M. Gr. n. Greek god of the underworld; Gr. adj. archeo ancient, also referring to Archaea. L. part. Hadesarchaeum, the archaeal god of the underworld. The type species is “Ca. Hadesararchaeum tengchongensis”. “Ca. Hadesararchaeum tengchongensis” (teng.chong.en’sis) originating from Tenghchong, a region of Yunnan Province, China. The type material is the metagenomic bin JZ-2 bin_199 (Ga0263248). “Methanourarchaeum” (Me.tha.no.ur’ar.chae.um) M. L. n. methanum methane; ur, primitive, original, referring to the deeply branching position of the organism in phylogenomic analyses; Gr. adj. archeo ancient, also referring to Archaea. L. part. Methanourarchaeum, the primitive methanogen. The type species is “Ca. Methanourarchaum thermotelluricum”. “Ca. Methanourarchaum thermotelluricum” (ther.mo.tel.lu’ri.cum). Gr. n. therme heat; L. n. telluricus, originating from the Earth; thermotelluricum L. adj. originating from hot Earth. The type material is the metagenomic bin JZ-1 bin_103 (Ga0263246). Phylogenomic analyses support the proposal for a new family inclusive of both “Ca. Hadesararchaeum tengchongensis” and “Ca. Methanourarchaum thermotelluricum”, Hadesarchaeacaceae (Ha.des.ar.ca’ce.ae) N.L. n. Hadesararchaeum type genus of the family; L. suff. -aceae ending to denote a family; N.L. fem. pl. n. Hadesarchaceae the family of the genus Hadesarchaeum. Similarly, a new order is proposed, Hadesarchaeales (Ha.des.ar.che.a’les) N.L. n. Hadesarchaeum type genus of the order; L. suff. -ales ending to denote an order; N.L. fem. pl. n. Hadesarchaeales the order of the genus Hadesarchaeum. A new class is proposed, Hadesarchaea (Ha.des.ar.ca’.a) N.L. n. Hadesararchaeum type genus of the class; Hadesarchaea the class of the genus Hadesarchaeum. A new phylum is proposed, Hadesarchaeota (Ha.des.ar.ca’.o.ta) N.L. n. Hadesarchaeum type genus of the phylum; L. suff. -ota ending to denote an phylum; N.L. fem. pl. n. Hadesarchaeaota the phylum of the genus Hadesarchaeum.

“Methanomixtatrophicum” (Me.tha.no.mix.ta.tro’phi.cum) M. L. n. methanum methane; M. L. adj. mixed, referring to H₂-dependent methanogenesis; N.L. neut. adj. trophicum (from Gr. neut. adj. trophikon) nursing, tending or feeding; Methanomixtatrophicum, the methanogen using mixed substrates. The type species is “Ca. Methanomixtatrophicum sinensis”. “Ca. Methanomixtatrophicum sinensis” (si.nen’sis). L. adj. originating from China. The type material is the metagenomic bin JZ-2 bin_168 (Ga0263247). Phylogenomic analyses support the proposal for a new family, Methanomixtatrophicaceae (Me.tha.no.mix.ta.tro’phi.ca’ce.ae) N.L. n. Methanomixtatrophicum type genus of the family; L. suff. -aceae ending to denote a family; N.L. fem. pl. n. Methanomixtatrophicaceae the family of the genus Methanomixtatrophicum.

“Methanoproducendum” (Me.tha.no.pro.du.cen’dum) M. L. n. methanum methane; M. L. adj. producer; L. part. Methanoproducendum, the methane producer. The type species is “Ca. Methanoproducendum senex”. “Ca. Methanoproducendum senex” (se’nex). L. n. old man, referring to the deep-branching position of the organism. The type material is the metagenomic bin GMQP bin_32 (Ga0263258). Phylogenomic analyses support the proposal for a new family, Methanoproducendacaceae (Me.tha.no.pro.du.cen’da’ce.ae) N.L. n. Methanoproducendum type genus of the family; L. suff. -aceae ending to denote a family; N.L. fem. pl. n. Methanoproducendacaceae the family of the genus Methanoproducendum.

“Methylarchaeum” (Me.thyl.ar.cha’um) M. L. n. methanum methane; methyl, referring to methylotrophic metabolism; Gr. adj. archeo ancient, also referring to Archaea. L. part. Methylarchaeum, the methane-consuming archaeon. The type species is “Ca. Methylarchaeum tengchongensis”. “Ca. Methylarchaeum tengchongensis” (teng.chong.en’sis) originating from Tengchong, a region of Yunnan Province, China. The type material is the metagenomic bin JZ-2 bin_220 (Ga0263250).