Guerrero-Cruz Simon, Vaksmaa Annika, Horn Marcus A, Niemann Helge, Pijuan Maite, Ho Adrian
Catalan Institute for Water Research (ICRA), Girona, Spain.
Universitat de Girona, Girona, Spain.
Front Microbiol. 2021 May 14;12:678057. doi: 10.3389/fmicb.2021.678057. eCollection 2021.
Methane is the final product of the anaerobic decomposition of organic matter. The conversion of organic matter to methane (methanogenesis) as a mechanism for energy conservation is exclusively attributed to the archaeal domain. Methane is oxidized by methanotrophic microorganisms using oxygen or alternative terminal electron acceptors. Aerobic methanotrophic bacteria belong to the phyla Proteobacteria and Verrucomicrobia, while anaerobic methane oxidation is also mediated by more recently discovered anaerobic methanotrophs with representatives in both the bacteria and the archaea domains. The anaerobic oxidation of methane is coupled to the reduction of nitrate, nitrite, iron, manganese, sulfate, and organic electron acceptors (e.g., humic substances) as terminal electron acceptors. This review highlights the relevance of methanotrophy in natural and anthropogenically influenced ecosystems, emphasizing the environmental conditions, distribution, function, co-existence, interactions, and the availability of electron acceptors that likely play a key role in regulating their function. A systematic overview of key aspects of ecology, physiology, metabolism, and genomics is crucial to understand the contribution of methanotrophs in the mitigation of methane efflux to the atmosphere. We give significance to the processes under microaerophilic and anaerobic conditions for both aerobic and anaerobic methane oxidizers. In the context of anthropogenically influenced ecosystems, we emphasize the current and potential future applications of methanotrophs from two different angles, namely methane mitigation in wastewater treatment through the application of anaerobic methanotrophs, and the biotechnological applications of aerobic methanotrophs in resource recovery from methane waste streams. Finally, we identify knowledge gaps that may lead to opportunities to harness further the biotechnological benefits of methanotrophs in methane mitigation and for the production of valuable bioproducts enabling a bio-based and circular economy.
甲烷是有机物厌氧分解的最终产物。有机物转化为甲烷（甲烷生成）作为一种能量守恒机制，完全归因于古菌域。甲烷被利用氧气或替代末端电子受体的甲烷营养微生物氧化。好氧甲烷营养细菌属于变形菌门和疣微菌门，而厌氧甲烷氧化也由最近发现的厌氧甲烷营养菌介导，它们在细菌域和古菌域均有代表。甲烷的厌氧氧化与硝酸盐、亚硝酸盐、铁、锰、硫酸盐和有机电子受体（如腐殖质）作为末端电子受体的还原作用相耦合。本综述强调了甲烷营养作用在自然和受人为影响的生态系统中的相关性，重点关注环境条件、分布、功能、共存、相互作用以及可能在调节其功能中起关键作用的电子受体的可用性。对生态、生理、代谢和基因组学关键方面进行系统概述，对于理解甲烷营养菌在减少甲烷排放到大气中的贡献至关重要。我们重视好氧和厌氧甲烷氧化菌在微需氧和厌氧条件下的过程。在受人为影响的生态系统背景下，我们从两个不同角度强调甲烷营养菌当前和潜在的未来应用，即通过应用厌氧甲烷营养菌在废水处理中减少甲烷排放，以及好氧甲烷营养菌在从甲烷废物流中回收资源方面的生物技术应用。最后，我们确定了知识空白，这些空白可能带来机会，进一步利用甲烷营养菌在减少甲烷排放和生产有价值生物产品方面的生物技术益处，从而实现基于生物的循环经济。
