Page 209 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Figure 2. PCoA analysis on a) the taxonomic profile and b) the functional profile of the original (blue squares) and incubated (red circles) samples of the active layer (AL), transition layer (TL), and permafrost (PF). PC1 and PC2 indicate the first two principal coordinate axes. Percentages between brackets indicate the variability explained by the respective PC axis.
Taxonomic shifts within the bacterial population
The bacterial domain is dominated by members of the Bacteroidetes, Firmicutes and Proteobacteria which together made up an average relative abundance of 53.7% (Fig. 3). The long-term incubation resulted in an increase in the relative abundance of Bacteroidetes and Firmicutes in all layers, but especially in TL (by 6.3% and 4.3%) and PF (by 10.9% and 2.3%). In addition, Patescibacteria were more abundant in the incubated samples (average 10.0%) compared to the original samples (average 5.1%). On the class level, strong increases upon the incubation were observed for Parcubacteria, Microgenomatia, and Clostridia (Fig. 4a). By contrast, long-term incubation resulted in a decrease of Proteobacteria and Actinobacteria during the long-term incubation (by 6.1% and 5.8%). Acidobacteria showed a low abundance in the original samples (3.0%, 3.9% and 2.6% for AL, TL, and PF respectively) and were negligible (below 0.01%) at the end of the incubation. A complete overview of the bacterial community changes at phylum level for all layers is given in Table S1. On the class level, the strongest relative decreases were observed for V errucomicrobiae, Alphaproteobacteria, Actinobacteria, and Acidobacteria (Fig. 4a).
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