Brockarchaeota, a novel archaeal lineage capable of methylotrophy

Abstract

Single carbon (C1) compounds such as methanol, methylamines and formaldehyde are ubiquitous in nature and they are large components of the carbon cycle. In anoxic environments C1-utilizing microbes (methylotrophs) play an important role in controlling global carbon degradation. Currently described anaerobic methylotrophs are limited to methanogenic archaea, acetogenic bacteria, and sulfate-reducing bacteria. Here, we report the first archaeal lineage outside of methanogenic taxa that are capable of anaerobic methylotrophy. Phylogenetic analyses suggest these archaea form a new phylum within the TACK superphylum, which we propose be named Brockarchaeota. A survey revealed Brockarchaeota are globally distributed in geothermal springs. Metabolic inference from 15 metagenome-assembled genomes from hot springs and deep-sea sediments indicates that Brockarchaeota are strict anaerobes. They contain a variety C1 metabolisms including the methanol and trimethylamine methyltransferases system, the ribulose bisphosphate pathway coupled with the non-oxidative pentoses phosphate pathway, and reductive glycine pathway. Brockarchaeota have an incomplete methyl-branch of the Wood-Ljungdahl pathway probably used for formaldehyde oxidation, since they lack several core genes involved in methanogenesis including methyl-CoM reductases. Brockarchaeota also appear to play an important role in the breakdown of plant-derived polysaccharides, especially cellulose, starch and xylan. Their broad distribution and their capacity to use both C1 compounds and complex polysaccharides via anaerobic metabolism suggest that the Brockarchaeota occupy previously overlooked roles in carbon cycling.

Taxonomic and carbon metabolic diversification of Bathyarchaeia during its co-evolution history with the early Earth surface environment

“…However, it is unlikely for Bathyarchaeia, as the key gene coding for methylcoenzyme M reductase (MCR) in methanogenesis is absent in the majority of Bathyarchaeia lineages (see the next part for details). In addition, anaerobic respiration and acetogenesis are alternative pathways for metabolizing methanol (48) and methylamines (49). Accordingly, given the generally missing sulfate reduction or denitrification pathways but the prevalent acetate metabolism-involved genes (e.g., Ack, Pta and ACSS) in most Bathyarchaeia MAGs (Fig.…”

Culexarchaeia, a novel archaeal class of anaerobic generalists inhabiting geothermal environments

“…Nezhaarchaeota (8), and Ca. Brockarchaeota (9), were originally discovered in extreme geothermal habitats. While most of these lineages have no cultured representatives, they are often proposed to play important roles in biogeochemical cycles (2,10).…”