• Centre for Microbiology and Environmental Systems Science

  • CUBE - Computational Systems Biology

  • DOME - Microbial Ecology

  • EDGE - Environmental Geosciences

  • TER - Terrestrial Ecosystem Research


Latest publications

Assessing microbial residues in soil as a potential carbon sink and moderator of carbon use efficiency

A longstanding assumption of glucose tracing experiments is that all glucose is microbially utilized during short incubations of ≤2 days to become microbial biomass or carbon dioxide. Carbon use efficiency (CUE) estimates have consequently ignored the formation of residues (non-living microbial products) although such materials could represent an important sink of glucose that is prone to stabilization as soil organic matter. We examined the dynamics of microbial residue formation from a short tracer experiment with frequent samplings over 72 h, and conducted a meta-analysis of previously published glucose tracing studies to assess the generality of these experimental results. Both our experiment and meta-analysis indicated 30–34% of amended glucose-C (13C or 14C) was in the form of residues within the first 6 h of substrate addition. We expand the conventional efficiency calculation to include residues in both the numerator and denominator of efficiency, thereby deriving a novel metric of the potential persistence of glucose-C in soil as living microbial biomass plus residues (‘carbon stabilization efficiency’). This new metric indicates nearly 40% of amended glucose-C persists in soil 180 days after amendment, the majority as non-biomass residues. Starting microbial biomass and clay content emerge as critical factors that positively promote such long term stabilization of labile C. Rapid residue production supports the conclusion that non-growth maintenance activity can illicit high demands for C in soil, perhaps equaling that directed towards growth, and that residues may have an underestimated role in the cycling and sequestration potential of C in soil.

Geyer K, Schnecker J, Grand AS, Richter A, Frey S
2020 - Biogeochemistry, in press

A Large-Scale 3D Study on Transport of Humic Acid-Coated Goethite Nanoparticles for Aquifer Remediation

Humic acid-coated goethite nanoparticles (HA-GoeNPs) have been recently proposed as an effective reagent for the in situ nanoremediation of contaminated aquifers. However, the effective dosage of these particles has been studied only at laboratory scale to date. This study investigates the possibility of using HA-GoeNPs in remediation of real field sites by mimicking the injection and transport of HA-GoeNPs under realistic conditions. To this purpose, a three-dimensional (3D) transport experiment was conducted in a large-scale container representing a heterogeneous unconfined aquifer. Monitoring data, including particle size distribution, total iron (Fetot) content and turbidity measurements, revealed a good subsurface mobility of the HA-GoeNP suspension, especially within the higher permeability zones. A radius of influence of 2 m was achieved, proving that HA-GoeNPs delivery is feasible for aquifer restoration. A flow and transport model of the container was built using the numerical code Micro and Nanoparticle transport Model in 3D geometries (MNM3D) to predict the particle behavior during the experiment. The agreement between modeling and experimental results validated the capability of the model to reproduce the HA-GoeNP transport in a 3D heterogeneous aquifer. Such result confirms MNM3D as a valuable tool to support the design of field-scale applications of goethite-based nanoremediation.

Milica Velimirovic, Carlo Bianco, Natalia Ferrantello, Tiziana Tosco, Alessandro Casasso, Rajandrea Sethi, Doris Schmid, Stephan Wagner, Kumiko Miyajima, Norbert Klaas, Rainer U. Meckenstock, Frank von der Kammer, Bert Engelen, Thilo Hofmann
2020 - Water, 12: 1207

Carbonates and cherts as archives of seawater chemistry and habitability on a carbonate platform 3.35 Ga ago: Insights from Sm/Nd dating and trace element analysis from the Strelley Pool Formation, Western Australia

Carbonates and cherts in the 3.35 billion-year-old Strelley Pool Formation (Fm.; Australia) host stromatolites that are among the oldest remnants of life on Earth. However, it is still not entirely clear whether these mineral phases are authigenic precipitates, and whether they represent reliable geochemical archives of early Earth environments. Here we present major/trace-element and Nd-isotope data of stromatolitic carbonates, associated crystal-fan carbonates, and cherts in the Strelley Pool Fm. (i) to assess the reliability of these chemical sediments as geochemical archives of the fluids from which they precipitated, (ii) to date the time of formation of carbonate and silica phases, and (iii) to trace the sources of elements prevailing in microbial habitats 3.35 Ga ago.

Stromatolitic carbonates plot together with the stratigraphically underlying Marble Bar cherts on a Sm-Nd regression line yielding 3253 ± 320 Ma. In contrast, associated crystal-fan carbonates together with altered Marble Bar cherts yield 2718 ± 220 Ma, suggesting that their Sm-Nd isotope system was reset after deposition. Both types of carbonates, as well as white cherts, show shale-normalized rare earth element and yttrium patterns (REYSN; with the exception of redox-sensitive Ce and Eu and heavy REYSN to middle REYSN depletion) that are parallel to those of modern seawater, indicating a predominantly seawater-derived origin. Positive EuSN anomalies (2.1–2.4), combined with heterogeneous ɛNd3.35Ga values between −3.2 and +5.8 within individual alternating stromatolite laminae, further support that the dissolved fraction of seawater on the ancient carbonate platform was variably affected by both continental weathering and high-temperature hydrothermal fluids contributing elements of both young mafic or older felsic rocks. In conclusion, trace element and Nd isotope data presented here match well with the depositional environment, as characterized based on lithological, geochemical, and stratigraphic relationships, on an early continent, showing at least episodic emergence above the sea level, supporting microbial life on a shallow marine platform.

    Sebastian Viehmann. Joachim Reitner, NathalieTepe, Simon V. Hohl, Martin Van Kranendonk, Thilo Hofmann, Christian Koeberl, Patrick Meister
    2020 - Precambrian Research, 344: 105742

    Lecture series

    Environmental Geochemistry of Dissolved Mn(III) Species: Where are we now?

    Prof. Dr. Zimeng Wang
    Department of Environmental Sciences & Engineering, Fudan University, China
    17:00 h

    Defining and controlling gut microbial gene products for therapeutic gain

    Matthew Redinbo
    University of North Carolina, USA
    12:00 h

    Organic Biomolecule-Mineral Interactions in the Origins of Life

    Prof. Dr. Nita Sahai
    Department of Polymer Science, University of Akron, USA
    17:00 h