Sybille Zitzmann

The nitrogen and sulfur cycle of big colorless sulfur bacteria

In cooperation with the Max-Planck-Institute for Marine Microbiology this project is integrated within the project "Oxygen minimum zones in high-productiv regimes".
The discovery of a new group of sulfide-oxidizing bacteria that couple the oxidation of sulfide to the reduction of nitrate to ammonium has added a new pathway to the benthic sulfur cycle. But only little is known about the role of the big sulfur bacteria (mainly Thiomargarita spp. and Beggiatoa spp.), which occur in high densities in the surface sediments of Namibia and elsewhere, in the sulfur and nitrogen cycles of these diatom oozes. The aims of our studies are the enquiry of the contribution of the big colorless sulfur bacteria to the cycling of nitrogen and sulfur in the present and past. To get a better inside in the physiological possibilities of these bacteria we will conduct 15N and 35S enrichment experiments. We will also investigate the stable isotopes composition (nitrate and ammonium) of the bacteria and within the sediments to see if a fractionation takes place caused by these bacteria so we aquire an isotopic imprint, which is useful as a proxy for geological reconstruction of ancient environmental conditions.

This project is supervised by Volker Brüchert and Bo Barker Jørgensen