Page 128 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Chapter 5. Early Holocene carbon storage and microbial activity in North Sea peats
community (Bozkurt et al. 2001). The growth of Bathyarchaeota subgroup 8 (Bathy-8) on lignin suggests a key role of these species in the degradation of peat organic material (Yu et al. 2018), and based on chemical rate estimation, they have been identified as one of the most active phyla in deep sea sediments (Fry et al. 2008). These findings support the high relative abundance observed in our study and the potential central role of Bathyarchaeia in the peat sediments. However, further experimental evidence is needed to confirm the role of Bathyarchaeia.
Lokiarchaea may play an important role in microbial fermentation
Lokiarchaeal sequences were highly abundant in the three samples of Vittorio Z, and this location also showed the highest CH4 accumulation values (Fig. 5). Genome-based studies have indicated that their cellular machinery includes eukaryotic signature proteins, a cytoskeleton and phagocytic potential, suggesting Lokiarchaea are “missing link” microorganisms between prokaryotes and eukaryotes (Spang et al. 2015). Lokiarchaea have not been previously detected in peat sediments, but a previous 16S rRNA gene and metagenome-based study of sub-seafloor sediments of the Costa Rica Margin also found Lokiarchaeota among the major microbial phyla; thus, Lokiarchaeota may be indicative of a marine environment (Martino et al. 2019).
Genomic analyses of “Candidatus Lokiarchaeota” have indicated an acetogenic lifestyle, hydrogen dependency and mixotrophic potential (Sousa et al. 2016; Spang et al. 2019). Similarly, metabolic activity analyses of Namibian shelf sediments have revealed potential for homoacetogenesis (Orsi et al. 2020). Populations of Lokiarchaea may provide important metabolic functions in organic matter degradation and methanogenic microbial guilds in marine sediments.
Candidate JS1 phylum bacteria dominate the potentially heterotrophic bacterial community
The JS1 lineage is a subgroup of the candidate phylum Atribacteria (Nobu et al. 2016a). Metabolic reconstructions indicate their potential for fermentative metabolism and syntrophic acetate oxidation (Lee et al. 2018), and several studies have indicated they are abundant within marine sediments (Fry et al. 2008; Lee et al. 2018). Studies in the Skagerrak, the German Wadden Sea and the Benguela Upwelling System showed that the upper sediment layers were
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