Precambrian fossils of fungi are sparse, and the knowledge of their early evolution and the role they played in the colonization of land surface are limited. Here, we report the discovery of fungi fossils in a 810 to 715 million year old dolomitic shale from the Mbuji-Mayi Supergroup, Democratic Republic of Congo. Syngenetically preserved in a transitional, subaerially exposed paleoenvironment, these carbonaceous filaments of ~5 μm in width exhibit low-frequency septation (pseudosepta) and high-angle branching that can form dense interconnected mycelium-like structures. Using an array of microscopic (SEM, TEM, and confocal laser scanning fluorescence microscopy) and spectroscopic techniques (Raman, FTIR, and XANES), we demonstrated the presence of vestigial chitin in these fossil filaments and document the eukaryotic nature of their precursor. Based on those combined evidences, these fossil filaments and mycelium-like structures are identified as remnants of fungal networks and represent the oldest, molecularly identified remains of Fungi.

The coprecipitation of organic carbon with iron minerals is important for its preservation in soils and sediments, but the mechanisms for carbon-iron interactions and thus the controls on organic carbon cycling are far from understood. Here we coprecipitate carboxylic acids with iron (oxyhydr)oxide ferrihydrite and use near-edge X-ray absorption fine structure spectroscopy and wet chemical treatments to determine the relationship between sequestration mechanism and organic carbon stability against its release and chemical oxidative remineralisation. We show that organic carbon sequestration, stabilisation and persistence increase with an increasing number of carboxyl functional groups. We suggest that carboxyl-richness provides an important control on organic carbon preservation in the natural environment. Our work offers a mechanistic basis for understanding the stability and persistence of organic carbon in soils and sediments, which might be used to develop an overarching relationship between organic functional group-richness, mineral interactions and organic carbon preservation in the Earth system.

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Following our systematic investigations on the durability of solid oxide fuel cell (SOFC) components (Bozzini, B.; Tondo, E.; Prasciolu, M.; Amati, M.; Kazemian, M.; Gregoratti, L.; Kiskinova, M. ChemSusChem, http://dx.doi. org/10.1002/cssc.201100140), the present in situ scanning photoelectron microscopy study is focused on the redox behavior of Ni−Cu bilayers in contact with Cr, representing the anodic material and interconnects for SOFCs, respectively.The experiments with this model cell, using yttria-stabilized zirconia (YSZ) electrolyte, were carried out in 2 × 10 −6 mbar O 2 at 650°C at open circuit potential (OCP) and under applied potential. The elemental images and the spectra from selected parts of the cell have revealed dramatic compositional and morphological changes under OCP conditions, yielding Ni−Cu islands covered with NiO in the electrode region and a NiO network in the YSZ electrolyte region. The Ni reduction dynamics as a function of applied potential is followed by continuous monitoring of the evolution of the Ni 2p spectra in different regions, which allowed the location of electrochemically active areas of the half-cell upon cathodic polarization. It was shown that after electrochemical reduction the reoxidation at OCP results in notable morphology alterations of the triple-phase contact region, which can be related to the empirically observed degradation of catalytic performance.

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