Iron (Fe) concentrations are increasing in lakes on a wide geographical scale, contributing to recent browning of lake waters. As available time series on lake-water Fe concentrations are relatively short, covering the past few decades only, varved lake sediments may provide extended and precisely dated records to study temporal Fe dynamics in lakes in response to environmental drivers, such as changes in catchment land use an...

Summary Bacteria in the order ‘ Candidatus Brocadiales’ within the phylum Planctomycetes ( Planctomycetota ) have the remarkable ability to perform anaerobic ammonium oxidation (anammox). Two families of anammox bacteria with different biogeographical distributions have been reported, marine Ca . Scalinduaceae and freshwater Ca . Brocadiaceae. Here we report evidence of three new species within a novel genus and family of anam...

Summary A large fraction of nitrogen (N) in forest soils is present in mineral‐associated proteinaceous compounds. The strong association between proteins and minerals limits microbial accessibility to this source, which is a relatively stable reservoir of soil N. We have shown that the ectomycorrhizal (ECM) fungus Paxillus involutus can acquire N from iron oxide‐associated proteins. Using tightly controlled isotopic, spectros...

Summary Soil organic matter (SOM) constitutes the largest terrestrial C pool. An emerging, untested, view is that oxidation and depolymerization of SOM by microorganisms promote the formation of SOM‐mineral associations that is critical for SOM stabilization. To test this hypothesis, we performed laboratory‐scale experiments involving one ectomycorrhizal and one saprotrophic fungus that represent the two major functional group...

Summary Soils in boreal forests contain large stocks of carbon. Plants are the main source of this carbon through tissue residues and root exudates. A major part of the exudates are allocated to symbiotic ectomycorrhizal fungi. In return, the plant receives nutrients, in particular nitrogen from the mycorrhizal fungi. To capture the nitrogen, the fungi must at least partly disrupt the recalcitrant organic matter–protein comple...