Ecophysiology of peat ammonia oxidizing archaea and their impact on nitrification and ecosystem functioning in fen peatlands

• Applicant: Dr. Haitao Wang
• Subject Area: Microbial Ecology and Applied Microbiology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544005677

Ammonia oxidizing archaea (AOA) are globally abundant and play important roles in soil nitrogen cycling. They are responsible for aerobic ammonia oxidation, the first and rate-limiting step of nitrification, particularly in acidic soils. Peatlands are water-logged wetlands with high levels of soil organic carbon and have been subject to drainage for agricultural uses. Rewetting is an endeavor to prevent carbon loss from the drained peatlands, which however introduces novel ecosystems. So far, knowledge about nitrogen-cycling in these peatlands remains scarce. In previous studies, we found an abundant and diverse AOA community in a pair of drained and rewetted fen peatlands in northern Germany. From these peat soils, we successfully enriched three distinct AOA, covering all major AOA lineages. When looking at their dynamics in the field, intriguing patterns were observed, as some of them showed higher abundance in the deeper peat layer or in the rewetted site. This is contrary to general expectation that they prefer more aerobic conditions for their metabolisms. This paradox could be explained by a recent breakthrough, revealing that a well-known marine AOA can produce oxygen for ammonia oxidation under oxygen-depleted conditions. Therefore, we aim to isolate and characterize these enriched peat AOA, and test whether they are able to produce oxygen under oxygen-limited conditions, thus explaining the observed patterns. We will also use co-cultures to test whether these AOA will support other nitrifying microorganisms under oxygen-limited conditions, thereby completing nitrification. Moreover, we will apply the AOA culture to fresh peatland soils under different water conditions in microcosms to identify aerobic nitrification and its impact on ecosystem functioning in fen peatland soils in response to oxygen limitation. State-of-the-art molecular techniques, i.e., qPCR, metagenomic sequencing, amplicon sequencing, quantitative double-RNA metatranscriptomic approach, stable isotope signatures and isotopomeres of N2O, will be used to construct genomes and study microbiome compositions and functions, trophic interactions as well as N2O sources and emissions. The proposed research will shed light on whether oxygen production is a common feature among different AOA especially those from terrestrial ecosystems. This will contribute new insights to the role of AOA in ecosystem functioning.

• DFG Programme: Research Grants
• International Connection: Austria
• Cooperation Partners: Professorin Dr. Christa Schleper; Professorin Dr. Nicole Wrage-Mönnig