Ombrotrophic bogs accumulate large stores of soil carbon that eventually decompose to carbon dioxide and methane. Carbon accumulates because Sphagnum mosses slow microbial carbon decomposition processes, leading to the production of labile intermediate compounds. Acetate is a major product of Sphagnum degradation, yet rates of hydrogenotrophic methanogenesis far exceed rates of aceticlastic methanogenesis, suggesting that alternative acetate mineralization processes exist. Two possible explanations are aerobic respiration and anaerobic respiration via humic acids as electron acceptors. While these processes have been widely observed, microbial community interactions linking Sphagnum degradation and acetate mineralization remain cryptic. In this work, we use ordination and network analysis of functional genes from 110 globally distributed peatland metagenomes to identify conserved metabolic pathways in Sphagnum bogs. We then use metagenome-assembled genomes (MAGs) from McLean Bog, a Sphagnum bog in New York State, as a local case study to reconstruct pathways of Sphagnum degradation and acetate mineralization. We describe metabolically flexible Acidobacteriota MAGs that contain all genes to completely degrade Sphagnum cell wall sugars under both aerobic and anaerobic conditions. Finally, we propose a hypothetical model of acetate oxidation driven by changes in peat redox potential that explain how bogs may circumvent aceticlastic methanogenesis through aerobic and humics-driven respiration.

营养沼泽积累了大量的土壤碳，最终分解成二氧化碳和甲烷。碳积累是因为泥炭藓减缓微生物碳分解过程，导致产生不稳定的中间化合物。乙酸盐是泥炭藓降解的主要产物，但氢营养产甲烷的速率远远超过乙酸弹性产甲烷的速率，这表明存在替代的乙酸盐矿化过程。两种可能的解释是有氧呼吸和通过腐植酸作为电子受体的无氧呼吸。虽然这些过程已被广泛观察，但连接泥炭藓的微生物群落相互作用降解和醋酸盐矿化仍然是神秘的。在这项工作中，我们使用来自全球分布的 110 个泥炭地宏基因组的功能基因的排序和网络分析来识别泥炭藓沼泽中的保守代谢途径。然后，我们使用来自纽约州泥炭藓沼泽McLean Bog 的宏基因组组装基因组 (MAGs)作为当地案例研究，以重建泥炭藓降解和醋酸盐矿化的途径。我们描述了具有完全降解泥炭藓的所有基因的代谢灵活的酸杆菌门MAG有氧和无氧条件下的细胞壁糖。最后，我们提出了一个由泥炭氧化还原电位变化驱动的乙酸盐氧化假设模型，该模型解释了沼泽如何通过有氧和腐殖质驱动的呼吸作用来规避乙酸产甲烷。