232 Chapter 8 PHD OUTCOMES Anaerobic methanotrophs play a crucial role in regulating the emission of the potent greenhouse gas methane in natural sediments and some engineered ecosystems such as Waste Water Treatment Plants (WWTPs). In this final Chapter 8, the essential findings regarding the resilience and adaptation of anaerobic methanotrophs to eutrophication and climate change-derived stressors - specifically salinity and sulfide - in coastal ecosystems are synthesized. Conclusions also include insights into the metabolic flexibility of anaerobic methanotroph “Ca. Methanoperedens”, particularly in relation to sulfate-dependent anaerobic oxidation of methane (S-AOM) and sulfide tolerance in meromictic Lake Cadagno. In addition, the methodological biases and strengths that were encountered throughout this dissertation are discussed. Finally, we propose future directions for research on stress adaptation in anaerobic methanotrophs. The key outcomes of this PhD research are the following: 1. The choice of omics’ methods matters and shapes the outcome of studies. 2. Sulfide controls anaerobic methane oxidation in eutrophic coastal sediments (Chapter 2). 3. Contrasting sulfide and nitrogen loading select for distinct nitrogen reduction processes by chemolithotrophic methane-oxidizing microbial communities (Chapter 3). 4. Nitrogen deprivation and sulfide toxicity disrupt nitrogen cycling but highlight the resilience of the methanotrophic community (Chapter 4). 5. Sulfide inhibits “Ca. Methanoperedens” activity and new detoxification mechanisms are proposed (Chapter 5). 6. Freshwater “Ca. Methanoperedens” survives under marine salinities via N(ε)- acetyl-β-L-lysine accumulation (Chapter 6). 7. “Ca. Methanoperedens” is most likely involved in S-AOM in meromictic Lake Cadagno (Chapter 7).
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