Microbial controls of fen peatland carbon turnover (MicroFen)

• Applicants: Dr. Tjorven Hinzke; Dr. Bruno Hüttel; Professor Dr. Klaus-Holger Knorr
• Subject Area: Microbial Ecology and Applied Microbiology ; Metabolism, Biochemistry and Genetics of Microorganisms
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 522593772

Peatlands are a globally important carbon (C) sink. C storage in peat takes place when organic matter production exceeds decomposition by microbes. Despite this pivotal role of the peat microbiome in peatland C fluxes, which microbiome functions are key in biomass turnover, and how they relate to environmental conditions, are largely unresolved questions. This holds true especially for ground-and surface-water-fed peatlands, called fens, and in the face of rapidly changing environmental conditions due to anthropogenic impacts, foremost climate change. Therefore, we aim to elucidate how the active fen microbiome controls biomass turnover in fens. We focus on the interactions between fen microbiome functions, available substrate, and terminal electron acceptors for respiration. Our main hypothesis is that the unique conditions in peatlands, merging traits of aquatic and terrestrial environments, lead to a similarly unique mixture of microbial generalists and specialists. This in turn leads to a substrate decomposition bottleneck effect – specialists have comparatively slower substrate turnover rates, causing accumulation of organic material. The severity of this bottleneck will decrease with drier, i.e., more terrestrial, conditions. To test our hypothesis, we will integrate taxonomic and functional information of fen microbiomes gained from microcosm experiments. We will identify key microbiome signatures, and use these to extrapolate our findings to field conditions. For that, we will incubate fen peat with substrates of different quality, using three oxygen regimes (anoxic, oxic, oxic-anoxic shift). Greenhouse gas production and electron donor and electron acceptor capacities will allow insight into microbial respiratory activity. Based on these experiments, we will conduct further in-depth analyses. We will analyze whether and how labile substrate leads to peat decomposition using C budgets and analyzing peat chemical structure. Comparing microbiome data under different conditions – amplicon as well as detailed metatranscriptomics and -proteomics data, combined with enzyme assays – will allow us to identify key microbiome signatures. At the same time, metatranscriptomics together with metagenomics, will provide the basis for metaproteomics, in terms of a comprehensive fen microbiome protein database. Incubations with 13C-labelled substrate combined with metaproteomics will enable us to track the C through the microbial community, generating close-up insights into key players under different conditions. We will use the identified key microbiome signatures to compare our laboratory findings with field conditions by analyzing fresh peat from fens differing in vegetation and from different peat depths. Our work will provide valuable insights into key players and -interactions between fen microbiomes and environmental conditions and how these impact C fluxes, especially in the face of increasing drought-rewetting cycles.

• DFG Programme: Research Grants