Carlsen Eira Catharine Lødrup, Wei Jing, Lejzerowicz Franck, Trier Kjær Sigrid, Westermann Sebastian, Hessen Dag O, Dörsch Peter, Eiler Alexander
Section for Aquatic Biology and Toxicology, Department of Biosciences, University of Oslo, 0371 Oslo, Norway.
Center for Biogeochemistry in the Anthropocene, University of Oslo, 0371 Oslo, Norway.
ISME Commun. 2025 Mar 3;5(1):ycaf009. doi: 10.1093/ismeco/ycaf009. eCollection 2025 Jan.
Redox conditions, influenced by the availability of oxygen, are expected to dictate the rate of CO and CH production and to shape the composition and metabolism of microbial communities. Here, we use thawing permafrost peat in thermokarst water under a gradient of initial O concentrations to experimentally cover the variability in redox conditions potentially found across thawing landscapes. The three main greenhouse gases, CO, CH and NO, responded differently to O absence. CO production along the O gradient could be modeled by the Michaelis Menten equation revealing a sharp decrease when oxygen dropped under 100 μM. Under anoxic conditions CO yield decreased by 98% and maximum net production rate by 85% when compared to oxic conditions during the 11 days after thaw. NO production was observed under anoxic conditions, while CH yield and CH accumulation rates did not differ across the redox gradient. The latter is due to the release of stored CH due to thawing. Differences between oxic and anoxic conditions were reflected in the microbial genomic composition, with changes in taxonomic and functional groups, such as NO reducers, fermenters, denitrifiers and sulfur reducers increasing under anoxic conditions. Genomic changes towards less efficient central metabolism further explained the CO production yields and rates limited by O availability as predicted by thermodynamics. Together with the Michaelis Menten models the metabolic reconstruction pinpoint to critical thresholds of CO release at suboxic conditions and thus need to be considered when explaining and modeling highly variable CO emissions across thawing landscapes.
受氧气可利用性影响的氧化还原条件，预计将决定一氧化碳（CO）和甲烷（CH）的产生速率，并塑造微生物群落的组成和代谢。在此，我们利用热喀斯特水中解冻的永久冻土泥炭，在初始氧浓度梯度下进行实验，以涵盖解冻区域可能存在的氧化还原条件变化。三种主要温室气体，即CO、CH和一氧化氮（NO），对缺氧的反应各不相同。沿氧梯度的CO产生可用米氏方程建模，结果显示当氧气降至100μM以下时急剧下降。与解冻后11天的有氧条件相比，在缺氧条件下，CO产量下降了98%，最大净产生速率下降了85%。在缺氧条件下观察到NO的产生，而CH产量和CH积累速率在氧化还原梯度上没有差异。后者是由于解冻导致储存的CH释放。有氧和缺氧条件之间的差异反映在微生物基因组组成上，分类和功能组发生了变化，如缺氧条件下NO还原菌、发酵菌、反硝化菌和硫还原菌增加。向效率较低的中心代谢的基因组变化进一步解释了如热力学预测的那样，受氧可利用性限制的CO产生量和速率。结合米氏模型，代谢重建确定了亚oxic条件下CO释放的临界阈值，因此在解释和解冻区域高度可变的CO排放建模时需要考虑这些因素。
