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DSSS: Microbial Element Cycling – The Big Picture

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Marc Strous is a Professor of Microbiology and Campus Alberta Innovates Chair at the Department of Geoscience, University of Calgary. He obtained his PhD at Delft University of Technology (The Netherlands) under supervision of Gijs Kuenen. During his PhD project, he pioneered the microbiology of anaerobic ammonium oxidation (anammox), and explored that exciting topic for many years. Later, he also discovered other "impossible" bacteria that couple methane oxidation to denitrification. Both discoveries originated from thermodynamic inferences and thermodynamics also provided the foundation for his present work on the forces of natural selection that shape microbial communities, that was initiated at the Max Planck Institute for Marine Microbiology in Bremen. His scientific discoveries received national and international recognition in the form of a many papers in high impact journals, a membership of the young academy of sciences of the Netherlands, a prestigious European Research Grant and the ISME young investigators award.


The microbiology that defines the cycling of the major chemical elements (carbon, oxygen, nitrogen, iron and sulfur) has been investigated both by studying microbes in isolation and by biogeochemical field observations. Here, I will present a different approach: the selective enrichment of natural microbial communities in continuous culture under defined sets of conditions. Continuous cultivation of microbial communities is a powerful tool to investigate how element cycling proceeds under near-natural conditions (dynamics, low substrate concentrations). The selected microbial processes are determined by mass balancing and off-line incubations and the identity and genetic repertoire of the associated populations is determined by metagenomics (e.g. next generation DNA sequencing). The results provide insight into the environmental controls on microbial competition and specialization. For example, I will show how different conditions lead to the selection for denitrification versus dissimilatory nitrate reduction to ammonium and shed light on a so far controversial phenomenon known as “aerobic denitrification”.