Safe geological disposal of radioactive waste requires a thorough understanding of geochemical conditions in the host formation. Boom Clay is a potential candidate in Belgium, where active methanogenesis has been detected in its deep subsurface, influencing the local geochemistry. However, the pathways driving this process and the characteristics of the methanogenic archaea involved remain unclear. We isolated a distinct archaeal strain from Boom Clay pore water and characterized it geno‐ and phenotypically. Isolate TD41E1‐1 belongs to a novel species of the Methanosarcina genus, for which the name Methanosarcina hadiensis sp. nov. is proposed. TD41E1‐1 cells are coccus‐shaped, irregularly sized cells enveloped by extracellular polymer substances. Growth and substrate utilization experiments and genomic analysis demonstrated that the strain prefers methylated compounds or hydrogen as substrates for methane production. Although it possesses a complete acetoclastic pathway, no growth was observed in the presence of acetate in the tested conditions. Based on its phylogenetic relation to other known Methanosarcina species and on the presence of c‐type cytochromes, it can be concluded that the strain likely occupies an intermediate position between type I and type II Methanosarcina species. These findings provide valuable insights for assessing Boom Clay's suitability for geological disposal of radioactive waste.

中文翻译：

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一种新型甲烷菌 Methanosarcina hadiensis sp. nov. 的分离和表征。来自地下 Boom 粘土孔隙水


放射性废物的安全地质处置需要对宿主地层中的地球化学条件有透彻的了解。Boom Clay 是比利时的一个潜在候选者，在其地下深处检测到活跃的甲烷生成，影响了当地的地球化学。然而，驱动这一过程的途径和所涉及的产甲烷古细菌的特征仍不清楚。我们从 Boom Clay 孔隙水中分离出一种独特的古细菌菌株，并对其进行基因和表型表征。分离物 TD41E1-1 属于 Methanosarcina 属的一个新种，其名称为 Methanosarcina hadiensis sp. nov。被提议。TD41E1-1 细胞是球状、大小不规则的细胞，被细胞外聚合物物质包裹。生长和底物利用实验以及基因组分析表明，该菌株更喜欢甲基化化合物或氢作为甲烷生产的底物。尽管它具有完整的乙酰碎屑途径，但在测试条件下，在乙酸盐存在下未观察到生长。根据其与其他已知甲烷肉菌属物种的系统发育关系以及 c 型细胞色素的存在，可以得出结论，该菌株可能占据 I 型和 II 型甲烷肉菌属之间的中间位置。这些发现为评估 Boom Clay 是否适合地质处置放射性废物提供了有价值的见解。