Page 65 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Table 1. Characteristics of the four metagenome-assembled genomes (MAGs) with a completeness >95%. Taxonomy sister lineage, GC content, completeness, redundancy, strain heterogeneity and genome size were assessed by CheckM. Percentage coverage data provides the average aligned read coverage for each sampling location per MAG. AS: adjacent soil; DL: deposit layer.
CheckM taxonomy sister lineage (Order)
GC (%)
Complete- Redun- Hetero- Genome AS aligned DL aligned
Methanobacteriales 32.7 Coriobacteriales 66.4 Syntrophobacterales 45.7 Coriobacteriales 64.3
98.9 1.1 100 2.18 0.1 8.7 96.9 9.0 41.2 2.48 1.5 9.2 96.8 1.3 0.0 3.32 0.0 18.1 95.0 4.7 15.8 2.70 0.1 11.3
3
ness (%)
dancy (%)
geneity (%)
size (Mbp)
reads (%)
reads (%)
Clostridiales are common anaerobic soil inhabitants that can metabolize a wide variety of complex carbohydrates, including cellulose, leading to the production of ethanol, acetate, CO2, and H2, which are essential intermediates in biological organic carbon cycling (Warnick, Methé and Leschine 2002; Tracy et al. 2012). Flavobacteriales are often detected in low-temperature, organic-rich soils and sediments, where they are linked to changes in carbon availability (Aislabie et al. 2006; Campbell et al. 2010). A recent metagenomic study by Rasigraf et al. (2019) also found high relative abundances of Flavobacteriales in cooccurrence with methanogenic archaea in oligotrophic brackish sediments with large amounts of reactive iron. They were also detected in soil lignolytic communities that are essential for organic compound cycling (Pold, Melillo and DeAngelis 2015). This supports our observation of Flavobacteriales in sediments with plant-based organic matter and reactive iron species. Anaerolineales (average, 2.9%), Betaproteobacteriales (average, 2.4%) and Bacteroidales (average, 1.9%) were also detected in all samples. These orders include common soil inhabitants (Kuramae et al. 2012; Yun et al. 2012; Chemerys et al. 2014). Betaproteobacteria (Syntrophaceae) and Bacteroidales are indicators of soils with higher pH (>6.5) and relatively low C:N ratios (<12.5) (Kuramae et al. 2012). Their occurrence matches with the buffered conditions and high organic matter contents of the sediments in this study. All three orders likely play a role in organic matter degradation, although their exact contributions remain unknown.
Deltaproteobacteria, Bacteroidetes, and Bathyarchaeota potentially have a central role in acetate metabolism
To study central carbon metabolism, we investigated acetate kinase (ackA) and acetyl- coenzyme A synthetase (ACS) gene diversity in DL and AS. Reads were extracted from the
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