However, in a study investigating the archaeal lipidome in the White Oak River estuary, the presence of the recently discovered butanetriol dibiphytanyl glycerol tetraethers correlated well with bathyarchaeotal abundance along the sediment depth (Meadoretal.2015). In this process, methane is not assimilated by Bathyarchaeota but serves as an energy source. The archaeal phylum Bathyarchaeota, which is composed of a large number of diverse lineages, is widespread and abundant in marine sediments. Methanogens and acetogenic Clostridia are the most frequent basal-branching archaea and bacteria, respectively, in phylogenetic reconstructions reflecting the descendants of the last universal common ancestor; gene categories proposed for the last universal common ancestor also point to the acetogenic and methanogenic roots, reflecting its autotrophic lifestyle as H2-dependent and N2-fixing, utilizing the WoodLjungdahl pathway and originating from a hydrothermal environmental setting (Weissetal.2016). (Fig. The ability to use a wide range of substrates for energy conservation and biosynthesis, rather than a single reductive acetyl-CoA pathway, enhances the survival of Bathyarchaeota in energy-limited environments (Lazaretal.2016). The discovery of BchG of archaeal origin in the genomic content of Bathyarchaeota also suggests that an archaeon-based photosynthetic pathway might exist in nature, and that photosynthesis might have evolved before the divergence of bacteria and archaea (Mengetal.2009). Fillol M, Snchez-Melsi A, Gich F et al. [43] (Figure 4). Within Bathyarchaeota, the sequences were classified into six subclades according to . Methane metabolism pathways have been identified in members of phylum Bathyarchaeota and in the recently discovered phylum Verstraetearchaeota, placing the origin of methanogenesis before the divergence of Euryarchaeota (Evansetal.2015; Vanwonterghemetal.2016). Peat MCG group was represented with one sequence at 90% cutoff level (Xiangetal.2017). Barns SM, Delwiche CF, Palmer JD et al. Furthermore, another study demonstrated that the archaeal communities of the sulfatemethane transition zone at diffusion-controlled sediments of Aarhus Bay (Denmark) contain considerable amounts of Bathyarchaeota; the overall archaeal community structure did not change greatly during the experimentits diversity was lower after 6 months of incubation under heterotrophic conditions, with periodic modest sulfate and acetate additions (Websteretal.2011). However, their life strategies have remained largely elusive. Markers for individual pathway/function were scanned against genomes using the HMM and KEGG databases (Anantharamanetal.2016; Kanehisa, Sato and Morishima 2016; Spang, Caceres and Ettema 2017). These archaeal groups are the phylogenetically closest ones to the protoeukaryote that served as the mitochondrion-acquiring host; this gave rise to a hydrogen hypothesis that explains their hydrogen-dependent metabolism to address the mitochondrion acquisition and subsequent endosymbiont processes. Currently available bathyarchaeotal genomes (from GenBank, 29 November 2017 updated) with 16S rRNA gene sequences were labeled in the tree. 2017KZDXM071), and the Science and Technology Innovation Committee of Shenzhen (Grant No. To increase the permeability of the cell wall and obtain a good amplification signal, a 10-min 0.01 M HCl treatment may be employed (Kuboetal.2012).
