Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, 9220 Aalborg, Denmark.
Department of Biological and Chemical Engineering, Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus, Denmark.
Environ Sci Technol. 2024 Apr 16;58(15):6637-6646. doi: 10.1021/acs.est.3c07725. Epub 2024 Apr 5.
Methanogenesis is a critical process in the carbon cycle that is applied industrially in anaerobic digestion and biogas production. While naturally occurring in diverse environments, methanogenesis requires anaerobic and reduced conditions, although varying degrees of oxygen tolerance have been described. Microaeration is suggested as the next step to increase methane production and improve hydrolysis in digestion processes; therefore, a deeper understanding of the methanogenic response to oxygen stress is needed. To explore the drivers of oxygen tolerance in methanogenesis, two parallel enrichments were performed under the addition of H/CO in an environment without reducing agents and in a redox-buffered environment by adding redox mediator 9,10-anthraquinone-2,7-disulfonate disodium. The cellular response to oxidative conditions is mapped using proteomic analysis. The resulting community showed remarkable tolerance to high-redox environments and was unperturbed in its methane production. Next to the expression of pathways to mitigate reactive oxygen species, the higher redox potential environment showed an increased presence of selenocysteine and selenium-associated pathways. By including sulfur-to-selenium mass shifts in a proteomic database search, we provide the first evidence of the dynamic and large-scale incorporation of selenocysteine as a response to oxidative stress in hydrogenotrophic methanogenesis and the presence of a dynamic selenoproteome.
产甲烷作用是碳循环中的一个关键过程，在厌氧消化和沼气生产中得到了工业应用。虽然产甲烷作用在各种环境中自然发生，但需要无氧和还原条件，尽管已经描述了不同程度的氧气耐受性。微需氧被认为是提高甲烷产量和改善消化过程中水解的下一步；因此，需要更深入地了解产甲烷作用对氧气胁迫的反应。为了探索产甲烷作用对氧气耐受性的驱动因素，在没有还原剂的环境中添加 H/CO 并在氧化还原缓冲环境中添加氧化还原介体 9,10-蒽醌-2,7-二磺酸钠二钠的情况下，进行了两个平行的富集。使用蛋白质组学分析来绘制细胞对氧化条件的反应。所得群落对高氧化还原环境表现出显著的耐受性，并且其甲烷产量不受干扰。除了表达减轻活性氧物质的途径外，较高的氧化还原电位环境显示出更多的硒代半胱氨酸和与硒相关的途径存在。通过在蛋白质组学数据库搜索中包含硫到硒的质量转移，我们首次提供了在氢营养型产甲烷作用中硒代半胱氨酸作为对氧化应激的动态和大规模掺入的证据，以及动态硒蛋白组的存在。
