Nordcee, Department of Biology, University of Southern Denmark, Odense, Denmark.
Sci Rep. 2020 Jan 15;10(1):372. doi: 10.1038/s41598-019-57206-z.
The co-occurrence of Geobacter and Methanosarcinales is often used as a proxy for the manifestation of direct interspecies electron transfer (DIET) in the environment. Here we tested eleven new co-culture combinations between methanogens and electrogens. Previously, only the most electrogenic Geobacter paired by DIET with Methanosarcinales methanogens, namely G. metallireducens and G. hydrogenophilus. Here we provide additional support, and show that five additional Methanosarcinales paired with G. metallireducens, while a strict hydrogenotroph could not. We also show that G. hydrogenophilus, which is incapable to grow with a strict hydrogenotrophic methanogen, could pair with a strict non-hydrogenotrophic Methanosarcinales. Likewise, an electrogen outside the Geobacter cluster (Rhodoferrax ferrireducens) paired with Methanosarcinales but not with strict hydrogenotrophic methanogens. The ability to interact with electrogens appears to be conserved among Methanosarcinales, the only methanogens with c-type cytochromes, including multihemes (MHC). Nonetheless, MHC, which are often linked to extracellular electron transfer, were neither unique nor universal to Methanosarcinales and only two of seven Methanosarcinales tested had MHC. Of these two, one strain had an MHC-deletion knockout available, which we hereby show is still capable to retrieve extracellular electrons from G. metallireducens or an electrode suggesting an MHC-independent strategy for extracellular electron uptake.
在环境中,产电菌和产甲烷菌的共现通常被用作直接种间电子传递 (DIET) 表现的替代指标。在这里,我们测试了 11 种新的产甲烷菌和产电菌共培养组合。以前,只有最具电活性的产电菌通过 DIET 与产甲烷菌 Methanosarcinales 配对,即 G. metallireducens 和 G. hydrogenophilus。在这里,我们提供了更多的支持,并表明另外 5 种 Methanosarcinales 与 G. metallireducens 配对,而严格的氢营养型则不能。我们还表明,不能与严格的氢营养型产甲烷菌一起生长的 G. hydrogenophilus 可以与严格的非氢营养型 Methanosarcinales 配对。同样,一种不在 Geobacter 群之外的产电菌(Rhodoferrax ferrireducens)与 Methanosarcinales 配对,但与严格的氢营养型产甲烷菌不配对。与产电菌相互作用的能力似乎在 Methanosarcinales 中是保守的,Methanosarcinales 是唯一具有 c 型细胞色素的产甲烷菌,包括多血红素(MHC)。尽管如此,MHC 通常与细胞外电子转移有关,但并不是 Methanosarcinales 所特有的,在测试的 7 种 Methanosarcinales 中只有两种具有 MHC。在这两种中,有一种 MHC 缺失敲除菌株可用,我们在此表明,它仍然能够从 G. metallireducens 或电极中回收细胞外电子,这表明存在 MHC 独立的细胞外电子摄取策略。