Our research group has ample experience in studying sediment microorganisms using molecular techniques and activity-based methods. Using 16S rRNA (gene) amplicon sequencing, we identified microorganisms active in sulfur cycling in freshwater sediments, peatlands, and rice paddy fields (Hausmann et al., 2016, Wörner et al., 2016, Wörner et al., 2019). We are further well experienced to retrieve the genomes of key microbial species directly from the environment using metagenomics and follow their activity by metatranscriptomics or metaproteomics (Hausmann et al., 2018, Zecchin et al., 2018, Hausmann et al., 2019). These molecular approaches are regularly connected to activity assessments using analytical techniques ranging from HPLC and GC analyses to microsensor measurements (Pester et al., 2007, Hausmann et al., 2016, Wörner et al., 2016).
Prokaryotes inhabiting the deep subsurface of sediments account for more than half of all microbial cells in aquatic environments. While easily degradable substrates decrease rapidly with depth and age of sediments, the deep subsurface still contains microorganisms actively involved in biogeochemical processes. However, almost nothing is known about this habitat in lake environments and its relation to the paleolimnology of microorganisms. Here, we aim to characterize surface and subsurface sediments of Lake Nam Co using biogeochemical and molecular techniques. Biogeochemical activity gradients in surface sediments will be analyzed using microsensor measurements (redox, pH, oxygen, nitrate, sulfide, etc). Surface and subsurface sediments will be analyzed for their carbon mineralization activity using combined CO2 and CH4 measurements. In parallel, extracellular and intracellular DNA will be extracted separately (Torti et al., 2018) from 100 m-long sediment cores and analyzed by 16S rRNA gene amplicon sequencing. This approach will explore preserved microbial DNA in comparison to the alive microbial deep biosphere. Selected depth horizons will be analyzed in more detail using metagenomics and metatranscriptomics to retrieve population genomes of the most abundant deep biosphere microorganisms and to assess their in situ transcriptional activity.
Cooperation within TransTiP
Our Chinese partners will focus on the in-depth characterization of microbial communities in modern surface sediments of a wider variety of lakes with different hydrological parameters. The combination of the broader monitoring of modern surface sediments by our Chinese partners and the depth-resolved analysis of lake sediment records in Lake Nam Co conducted by this project will contribute to a detailed understanding of sediment microbiology in lakes on the Tibetan plateau.
Prof. Dr. Michael Pester, DSMZ
Prof. Dr. Antje Schwalb, TU Braunschweig
Prof. Dr. Yongqin Liu, ITP-CAS