Chair of Soil Science, TUM School of Life Sciences Weihenstephan, Technical University of Munich, Freising, Germany.
Research Unit Comparative Microbiome Analysis, Helmholtz Zentrum München, Neuherberg, Germany.
Environ Microbiol. 2022 Apr;24(4):1887-1901. doi: 10.1111/1462-2920.15921. Epub 2022 Feb 2.
Stimulating litho-autotrophic denitrification in aquifers with hydrogen is a promising strategy to remove excess NO , but it often entails accumulation of the cytotoxic intermediate NO and the greenhouse gas N O. To explore if these high NO and N O concentrations are caused by differences in the genomic composition, the regulation of gene transcription or the kinetics of the reductases involved, we isolated hydrogenotrophic denitrifiers from a polluted aquifer, performed whole-genome sequencing and investigated their phenotypes. We therefore assessed the kinetics of NO , NO, N O, N and O as they depleted O and transitioned to denitrification with NO as the only electron acceptor and hydrogen as the electron donor. Isolates with a complete denitrification pathway, although differing intermediate accumulation, were closely related to Dechloromonas denitrificans, Ferribacterium limneticum or Hydrogenophaga taeniospiralis. High NO accumulation was associated with the reductases' kinetics. While available, electrons only flowed towards NO in the narG-containing H. taeniospiralis but flowed concurrently to all denitrification intermediates in the napA-containing D. denitrificans and F. limneticum. The denitrification regulator RegAB, present in the napA strains, may further secure low intermediate accumulation. High N O accumulation only occurred during the transition to denitrification and is thus likely caused by delayed N O reductase expression.
利用氢气刺激含水层中的自养脱氮是去除过量 NO 的一种很有前途的策略，但它通常会导致细胞毒性中间产物 NO 和温室气体 N O 的积累。为了探究这些高浓度的 NO 和 N O 是否是由于基因组组成、基因转录调控或相关还原酶动力学的差异造成的，我们从受污染的含水层中分离出了氢营养型脱氮菌，进行了全基因组测序，并研究了它们的表型。因此，我们评估了 NO 、NO 、N O 、N 和 O 的动力学，因为它们耗尽了 O 并过渡到以 NO 为唯一电子受体、氢气为电子供体的脱氮过程。尽管具有不同的中间产物积累，但具有完整脱氮途径的分离物与 Dechloromonas denitrificans、Ferribacterium limneticum 或 Hydrogenophaga taeniospiralis 密切相关。高浓度的 NO 积累与还原酶的动力学有关。当有电子时，只有在含有 narG 的 H. taeniospiralis 中，电子才会流向 NO ，而在含有 napA 的 D. denitrificans 和 F. limneticum 中，电子则会同时流向所有脱氮中间产物。存在于 napA 菌株中的脱氮调节剂 RegAB 可能进一步确保了低中间产物积累。只有在过渡到脱氮时才会发生高浓度的 N O 积累，因此这可能是由于 N O 还原酶表达的延迟造成的。
