Département des Sciences Biologiques, Groupe de Recherche Interuniversitaire en Limnologie, Université du Québec à Montréal, Montréal, QC, H2X 1Y4, Canada.
Department of Environmental Science, SRM University AP, Amaravati, Andhra Pradesh, 522 502, India.
Nat Commun. 2022 Jan 10;13(1):43. doi: 10.1038/s41467-021-27718-2.
Previous stable isotope and biomarker evidence has indicated that methanotrophy is an important pathway in the microbial loop of freshwater ecosystems, despite the low cell abundance of methane-oxidizing bacteria (MOB) and the low methane concentrations relative to the more abundant dissolved organic carbon (DOC). However, quantitative estimations of the relative contribution of methanotrophy to the microbial carbon metabolism of lakes are scarce, and the mechanism allowing methanotrophy to be of comparable importance to DOC-consuming heterotrophy remained elusive. Using incubation experiments, microscopy, and multiple water column profiles in six temperate lakes, we show that MOB play a much larger role than their abundances alone suggest because of their larger cell size and higher specific activity. MOB activity is tightly constrained by the local methane:oxygen ratio, with DOC-rich lakes with large hypolimnetic volume fraction showing a higher carbon consumption through methanotrophy than heterotrophy at the whole water column level. Our findings suggest that methanotrophy could be a critical microbial carbon consumption pathway in many temperate lakes, challenging the prevailing view of a DOC-centric microbial metabolism in these ecosystems.
先前的稳定同位素和生物标志物证据表明，尽管甲烷氧化菌 (MOB) 的细胞丰度较低，且甲烷浓度相对较丰富的溶解有机碳 (DOC) 较低，但甲烷氧化作用是淡水生态系统微生物环中的一个重要途径。然而，定量估计甲烷氧化作用对湖泊微生物碳代谢的相对贡献仍然很少，并且允许甲烷氧化作用与消耗 DOC 的异养作用具有可比性的机制仍然难以捉摸。本研究使用培养实验、显微镜和六个温带湖泊中的多个水柱剖面，结果表明，由于 MOB 具有更大的细胞尺寸和更高的比活性，因此其作用比其丰度单独表明的要大得多。MOB 活性受到局部甲烷：氧气比的严格限制，在贫氧层体积分数较大的富 DOC 湖泊中，整个水柱水平的甲烷氧化作用比异养作用消耗更多的碳。我们的研究结果表明，在许多温带湖泊中，甲烷氧化作用可能是一种关键的微生物碳消耗途径，这挑战了这些生态系统中以 DOC 为中心的微生物代谢的普遍观点。
