Multiple stressor effects

In the environment, organisms are not just confronted with anthropogenic pollutants but often encounter additional stress by abiotic physical factors (increased light intensity, UV-radiation, temperature, pH changes) or biotic influences like pathogens, parasites or predators. This combination of chemical and non-chemical stresses is called multiple stressors and can strongly alter the tolerance of an organism to chemical pollutants. The combined effects of physical and chemical stresses depend very much on their cellular mode of action, because depending on their target site these stresses might have additive or even synergistic effects. We quantitatively and qualitatively study the effect of multiple stressors in different algal species, by e.g. monitoring changes in EC₅₀ values and analyzing cellular stress responses, respectively.

Combined effects of herbicides and UV radiation

Currently, we investigate the individual and combined effects of herbicides and UV radiation on the single celled green alga Chlamydomonas reinhardtii, by measuring a combination of physiological endpoints covering a wide range of cellular parameters (e.g. oxidative activity, chlorophyll fluorometry). Furthermore, we analyze the proteome composition of the organism at selected exposure conditions by applying a shotgun proteomics technique known as MudPIT (Multidimensional Protein Identification Technology [LINK]). This method enables us to identify specific protein markers for different stress conditions and to better understand the underlying modes of action.

Long-term adaptation to multiple stressors

In a second project, our focus lies on the long-term exposure of photosynthetic organisms to a combination of stresses in order to get information about the physiological and genetic adaptation to the different selection pressures caused by multiple stressors. Specifically, we want to know how the presence of a physical stressor affects the evolution of tolerance to anthropogenic pollutants. Thus, strains of the green alga Chlamydomonas reinhardtii and the cyanobacteria Synechocystis sp PCC6803 evolved after long-term adaptation to multiple stressors will be analyzed phenotypically for their tolerance to individual stress and genetically for the nature of the underlying mutations.