Medina-Armijo Cristy, Fernández Belén, Lucas Yolanda, Guivernau Miriam, Noguerol Joan, Marchesi Massimo, Martínez-Eixarch Maite, Alcaraz Carles, Prenafeta-Boldú Francesc X, Viñas Marc
Program of Sustainability in Biosystems, Institute of Agrifood Research and Technology (IRTA), Caldes de Montbui, Barcelona, Spain.
Program of Sustainability in Biosystems, Institute of Agrifood Research and Technology (IRTA), Caldes de Montbui, Barcelona, Spain.
Sci Total Environ. 2025 Jan 10;959:177941. doi: 10.1016/j.scitotenv.2024.177941. Epub 2025 Jan 2.
Paddy fields are a major anthropogenic source of global methane (CH) emissions, a powerful greenhouse gas (GHG). This study aimed at gaining insights of different organic and inorganic conductive materials (CMs) - biochar, fungal melanin, and magnetite - to mitigate CH emissions, and on their influence on key microbial populations, mimicking the postharvest season throughout the degradation of rice straw in microcosms under anaerobic conditions encompassing postharvest paddy rice soils from the Ebro Delta, Spain. Results showed that fungal melanin was the most effective CM, significantly reducing CH emissions by 29 %, while biochar amendment also reduced emissions by 10 %. Magnetite slightly increased CH production (3 %), but this result was non-significant compared to unamended control microcosms. All treatments (with and without CM) displayed the acetoclastic methanogenesis pathway according to isotopic signature of δC-CH, δC-CO and δH-CH. In the presence of CMs, the archaeal populations showed a major abundance of Methanobacteria, Methanosarcina, and Bathyarchaeia. Furthermore, linear discriminant analysis effect size (LefSe) revealed specific positive linkages between fungal melanin and electroactive bacteria like Geobacter, biochar with Clostridia, and magnetite with Thiobacillus, and specifically related with archaea, particularly Bathyarchaeia. Biochar may diversify volatile fatty acids (VFA) utilization leading to a final mitigation of cumulative CH emissions through complex microbial interactions in the later stages of incubation. In contrast, fungal melanin increased VFA production, while delaying CH production, and may have diverted the electron flow towards melanin quinone reduction, suppressing methanogenesis by oxidizing organic compounds. These results suggest that CMs might facilitate specific potential direct interspecies electron transfer (DIET) between syntrophic electroactive bacteria (i.e. Geobacter, Clostridia) and electroactive methanogens such as Methanosarcina and Methanobacteria, but also with alternative microbial populations with the potential for hampering methanogenesis in a certain extent.
稻田是全球甲烷（CH）排放的主要人为来源，甲烷是一种强大的温室气体（GHG）。本研究旨在深入了解不同的有机和无机导电材料（CMs）——生物炭、真菌黑色素和磁铁矿——对甲烷排放的缓解作用，以及它们对关键微生物种群的影响，通过模拟西班牙埃布罗三角洲收获后稻田土壤在厌氧条件下稻草降解整个收获后季节的微观世界情况。结果表明，真菌黑色素是最有效的CM，显著降低了29%的甲烷排放，而生物炭改良也使排放量降低了10%。磁铁矿略微增加了甲烷产量（3%），但与未改良的对照微观世界相比，这一结果并不显著。根据δC-CH、δC-CO和δH-CH的同位素特征，所有处理（有和没有CM）都显示出乙酸裂解产甲烷途径。在CMs存在的情况下，古菌种群中甲烷杆菌、甲烷八叠球菌和深古菌的丰度较高。此外，线性判别分析效应大小（LefSe）揭示了真菌黑色素与地杆菌等电活性细菌、生物炭与梭菌、磁铁矿与硫杆菌之间的特定正相关联系，特别是与古菌，尤其是深古菌的联系。生物炭可能使挥发性脂肪酸（VFA）的利用多样化，通过孵化后期复杂的微生物相互作用最终减轻累积甲烷排放。相比之下，真菌黑色素增加了VFA的产生，同时延迟了甲烷的产生，并且可能将电子流转向黑色素醌的还原，通过氧化有机化合物抑制产甲烷作用。这些结果表明，CMs可能促进了共生电活性细菌（即地杆菌、梭菌）与电活性产甲烷菌如甲烷八叠球菌和甲烷杆菌之间特定的潜在直接种间电子转移（DIET），但也与在一定程度上有可能阻碍产甲烷作用的其他微生物种群有关。
