215 Methanotrophic flexibility of “Ca. Methanoperedens” and SRB in meromictic Lake Cadagno Methanoperedens” sp. ZOTU1150 (Su et al., 2020). When compared to MAGs “Sed MAG Methanoperedens 1,2,3 and 5”, the “MnO2 MAG Methanoperedens” was rare in the original sediment, with around 0.007% relative abundance, and enriched to about 19.5 % in the incubations amended with manganese oxide (Supplementary Table 3 and 6). These incubations also favored the enrichment of non-canonical SRB from the Chloroflexota phylum and the order Anaerolineales. These organisms lack the dsrD subunit but include sulfide oxidoreductases (sqr) (classified as non-canonical SRB). The Anaerolineales contributed as much as 21% to the total metagenome (Supplementary Table 6). Recovered “Ca. Methanoperedens” spp. show EET potential To uncover the main metabolic traits and biogeography of the five Lake Cadagno “Ca. Methanoperedens” MAGs, we generated an annotated genome tree (Figure 3). “Sed MAG Methanoperedens 1 and 2” were most closely related to a groundwater “Ca. Methanoperedens” spp. (Figure 3). Conversely, “Sed MAG Methanoperedens 3 and 5” and “MnO2 MAG Methanoperedens” were more similar to “Ca. Methanoperedens” spp. from bioreactor enrichments amended with nitrate or metal oxides. Among them, “MnO2 MAG Methanoperedens” and the nitrateenriched “Ca. Methanoperedens BLZ2” exhibit the greatest similarity, sharing an AAI of 92% (Figure 3 and Supplementary Figure 2). Although phylogenetically closely affiliated with nitrate-reducing species, none of the Lake Cadagno “Ca. Methanoperedens” MAGs contained a nitrate reductase. We also screened for DNRA (dissimilatory nitrate reduction to ammonium) potential by searching for the functional genes for nitrite reductase (cytochrome c-552) (nrfA) and cytochrome c nitrite reductase small subunit (nrfH). In the sediment-associated “Ca. Methanoperedens” MAGs, we did not detect any nrfAH genes. However, in the “MnO2 MAG Methanoperedens”, we identified two nrfA genes (the catalytic subunit), but no nrfH was found, even in the unbinned fraction. All Lake Cadagno “Ca. Methanoperedens” MAGs included the full reverse methanogenesis pathway for anaerobic oxidation of methane and lacked cytosolic or energy conserving hydrogenases (Ech) (Supplementary Table 7). Closer inspection of the Lake Cadagno “Ca. 7
RkJQdWJsaXNoZXIy MTk4NDMw