251 Synthesis and discussion complex trade-off: controlling greenhouse gas emissions might succeed, but other ecosystem services could suffer. In Chapter 6, we propose two genetic markers, the kamA and ablB gene pair responsible for osmolyte N-acetyl-beta-l-lysine production, to track salinity adaptation in “Ca. Methanoperedens”. These could serve as useful tools for monitoring the impacts of increasing salinity for N-AOM performing anaerobic methanotrophs. In Chapter 5, we identified group III Dsr-LP sulfite reductases in “Ca. Methanoperedens” and some methanogens as putative sulfite detoxification marker. While Fsr group I sulfite reductases have successfully been used as a genetic marker for sulfite detoxification (Johnson & Mukhopadhyay, 2008; Susanti et al., 2019), Dsr-LP group III sulfite reductases might also offer a valuable marker for sulfite stress in “Ca. Methanoperedens” dominated methane-oxidizing ecosystems under salinity and sulfide stress. + Sulfate reduction Methanogenesis = = + CH4 CO2 H2S Organic C SO4 -2 ClFigure 3. Hypothesized effects of increased salinity, through sulfate and chloride (Cl-), on freshwater methane cycling communities and inhibition or stimulation of key processes: sulfate reduction and biological methane production (methanogenesis). “Ca. Methanoperedens” SPP. SYNTROPHIC PARTNERSHIP WITH SRB FOR S-AOM (CHAPTER 7) In Chapter 7, we explored the distinctive chemistry of the sulfate-rich freshwater Lake Cadagno, where we highlight the putative interaction between “Ca. 8
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