Fig. 3. Proposed mechanism and phylogeny of the main enzymes of the methyltransferase system MTS.

A Schematic model of the hypothesized methylotrophic metabolism in Brockarchaeota. C1 units of methanol and trimethylamine TMA are transferred to tetrahydrofolate (H₄F) via Methyltransferase System (MTS) to be ultimately converted to biomass or energy via convergent assimilatory routes for formaldehyde and formate reductive glycine pathway (rGlyP) and ribulose monophosphate pathway (RuMP). See more details in the text. B Phylogeny of methanol methyltransferases B subunit (MtaB). A total of seven methanol methyltransferase proteins were detected in Brockarchaeota and were aligned with 101 PFAM (PF12176) sequences, and 104 references obtained from Muñoz-Velasco et al.²⁸ and one Korarchaeota sequence from McKay et al.²⁷. C Phylogeny of trimethylamine methyltransferases A subunit (MttB). A total of 12 methanol methyltransferase proteins were detected in Brockarchaeota MAGs and were aligned with 24 PFAM (PF6253) sequences, and 18 references from Muñoz-Velasco et al.²⁸. The alignments were done using MAFFT v7.450 (default parameters) and refined with MUSCLE v3.8.425 (default parameters), then masked (50% gaps) in Geneious Prime 2020.0.5. The trees were generated using a maximum likelihood-based approach using RAxML v8.2.10 (Gamma+LG+F model, raxmlHPC-PTHREADS-AVX -f a -m PROTGAMMAAUTO -N autoMRE -p 12345 -x 12345 -s).