100 Chapter 3 Supplementary Table 1-3) or functional potential (Figure 1, Supplementary Figure 5 and Supplementary Table 5), which remained stable. The salinity increase tolerance observed for the freshwater “Ca. Methanoperedens BLZ2” sp. (Supplementary Figure 15) aligned with the acclimatation described in studies on brackish-acclimated (1.5%) cultures of “Ca. Methanoperedens nitroreducens” sp. (up to 3.7% salt-increase) (Frank et al., 2023). Likewise, the Methylomonadaceae family also included marine representatives (Supplementary Figure 16), suggesting potential for marine adaptations. To conclude, in this investigation we studied the effect of distinct nitrogen and sulfide addition to two coastal anoxic sediment microbiomes. We concluded that gammaproteobacteria are the most dominant and distinct group emphasizing their ability to deal with sulfide stress and that nitrate limitation stimulated DNRA that can accept more electrons per nitrate molecule compared to denitrification. The poorly characterized Methylomonadaceae genus Methylovulum and subgroup KS41 showed high metabolic flexibility and appeared to be strong competitors for nitrate reduction with the anaerobic methane oxidizer “Ca. Methanoperedens BLZ2” spp. Furthermore, we retrieved MAGs of Pseudomonadales IMCC2047 and Rugosibacter with very unusual Cu-MMOs whose functions need to be further evaluated. Data availability statement Raw 16S rRNA gene sequences and metagenomic reads and genomes have been uploaded to the European Nucleotide Archive (ENA) with project number PRJEB79860. Author contributions Conceptualization: MJEM, MSMJ and CUW; Methodology, Software, Formal Analysis and Investigation: MJEM, GJS; Writing – Original Draft: MJEM; Writing – Review & Editing – all authors; Supervision: ISA, MSMJ, CUW; Funding Acquisition: ISA, MSMJ, CUW.
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