183 Osmoregulation in freshwater anaerobic methane-oxidizing archaea under salt stress adaptation, we opted to slowly adapt the “Ca. Methanoperedens” enriched biomass until matching sea water conditions (3%) in a laboratory-scale sequencing batch bioreactor over the duration of ~ 12 weeks. This led to a methane oxidation activity retention at 1.5% and 3% salinities, whereas the archaea to bacteria cell percentages remained stable (with dry weights of: 1.58 mg/µL, 3.02 mg/µL and 0.38 mg/µL at salinities 0%, 1.5%, and 3%, respectively) (Fig. 1A). Reads or peptides (%) 0 1.5 3 Salinity (%) A B Cell counts (%) 0 1.5 0 1.5 0 1.5 Salinity (%) metagenome metatranscriptome metaproteome ‘Ca. Methanoperedens Vercelli Strain 1’ Geobacter Desulfobacterota GWZ25412 (uncultured) Gallionellaceae Unbinned Others Archaea Bacteria 45CO2/44CO2 (%) dw (mg/ml)-1 21 79 39 61 25 75 Figure 1. Methane oxidation potential at increasing salinities and meta-omics analysis of the microbial community. A Whole bioreactor activity assay with salinity (X-axis) and rates from approximately four-day cumulative percentage of 45C-CO 2 to 44C-CO 2 ratios in the headspace normalized by biomass dry weight (mg/ml) (Y-axis). Bar plots are filled with percentages of cell counts of bacteria and archaea, calculated from % 16S rRNA gene DNA copies per μl (purple, archaea; beige, bacteria). The timing for salinities varied: salinity 0%, 1.5% and 3% were sampled at weeks 0, 12 and 26, respectively. Salinity 0% to 1.5% increase was stepwise with a duration 12 weeks (0.25% per 2 weeks). Later, the bioreactor ran for 8 weeks at 1.5% salinity. Salinity 1.5% to 3% increase was also stepwise but quicker with a duration of 4 weeks (0.5% per week). B From left to right: metagenome bars refer to percentage of mapped reads of a certain MAG, metatranscriptome refers to transcripts per million (TPM) and metaproteome to relative abundance of top-3-peptides recovered. Only top population MAGs (>1% mapped reads) are plotted. 6
RkJQdWJsaXNoZXIy MTk4NDMw