Manganese reduction coupled to the oxidation of ammonium and sulphur - a geochemical curiosity or an important biogeochemical process?

虽然有机物氧化对生物地球化学循环的贡献已经被很好地理解，但大量假定的岩石营养过程迄今为止被忽视，但在环境中被认为是广泛和重要的。这些“新”过程的例子是还原硫或铵的氧化与锰的还原，这些过程是由本研究中研究的分离物驱动的。氨的锰依赖氧化产生氮气，可能造成海洋沉积物中90%的氮损失。因此，研究这一过程不仅对理解生物地球化学循环很重要。由于氮从系统中去除，不能用于初级生产，这种类型的厌氧氨氧化可能在避免富营养化方面发挥重要作用，特别是在沿海地区。同样，依赖于锰的硫化合物（单质硫，硫代硫酸盐）的氧化是一个迄今为止未知的过程。然而，它连接了海洋沉积物中硫和氧的元素循环，并有助于解决一个主要的生物地球化学问题：电子从硫化物转移到不同沉积层中空间分离的氧。由于这些化合物也存在于地下沉积物和含水层中，它们也可能为“深层生物圈”提供生命的基础。

While the contribution of organic matter oxidation to the biogeochemical cycles is well understood, a large number of putative lithotrophic processes has so far been overlooked but are assumingly widespread and important in the environment. Examples for these 'novel' processes are the oxidation of reduced sulphur species or ammonium coupled to manganese reduction, processes driven by the isolates investigated in this study. The manganese-dependent oxidation of ammonium produces nitrogen gas and may be responsible for 90% of the nitrogen loss in marine sediments. Investigating this process is, therefore, not only important for the understanding of the biogeochemical cycles. As nitrogen is removed from the system and not available for primary production, this type of anaerobic ammonium oxidation may play an important role in avoiding eutrophication, particularly in coastal areas. Similarly, manganese-dependent oxidation of sulphur compounds (elemental sulphur, thiosulphate) is a so far unknown process. However, it connects the element cycles of sulphur and oxygen in marine sediments and helps solving a major biogeochemical problem: the transfer of electrons from sulphide to oxygen spatially separated in different sediment layers. As these compounds are present also in subsurface sedments and aquifers they might also provide a basis for life for the 'Deep Biosphere'.