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Research interests

The hidden sulfur cycle in freshwater wetlands.

Freshwater wetlands are not only important for sustainability of biodiversity, water quality, flood protection, and recreational value but play an integral part in Earth’s biogeochemical cycles. In particular, they are considered key habitats in the upcoming climate change, influencing both positive and negative climate feedback cycles to the atmosphere in a warmer world. We study the hidden sulfur cycle in freshwater wetlands, which plays an important role in controlling the emission of the greenhouse gas methane from these environments. Our aim is to identify microorganisms that drive the hidden sulfur cycle in wetlands using amplicon sequencing and genome-centric metagenomics and to study their ecophysiology using metatranscriptomics and metaproteomics.

Ecophyiology of rare biosphere members.

Most of microbial diversity worldwide is captured in the rare biosphere. These microorganisms are characterized by relative population sizes of <0.1% in their respective environment. The rare biosphere is opposed by a much smaller number abundant microorganisms, which are typically made responsible for the major ecosystem functions in a habitat. However, there is accumulating evidence that the rare biosphere is not just a seed bank of microorganisms that are waiting to become active and numerically dominant upon environmental change, but harbors active microorganisms with important ecosystem functions. We study Desulfosporosinus species as important sulfate reducers in peatlands, which are able to compensate their very low natural abundance with high cell-specific sulfate reduction rates. This makes them an interesting model for highly active rare biosphere members that contribute to biogeochemical cycling of elements. Using comparative genomics and in situ metatranscriptomics, we aim to understand why Desulfosporosinus species are so successful as low abundance populations and what ecological forces prevent these microorganisms of becoming more abundant despite their success.

Nitrification in lake ecosystem

In this project, we study the influence of changing lake ecosystems on microorganisms driving the conversion of ammonia to nitrate in Lake Constance as an important prealpine lake and drinking water reservoir. Using process measurements of ammonia conversion, high-throughput 16S rRNA gene amplicon sequencing, metagenomics and metatranscriptomics, we are aiming to understand how the steadily increasing water temperatures in lakes influence population dynamics of nitrifying microorganisms and as a consequence the process of nitrification itself.