Michaela A. Mausz

Lipid membranes are essential for cellular life forming a barrier towards the environment. In phototrophic organisms such as cyanobacteria and eukaryotic microalgae they are also a key component of thylakoid membranes and chloroplasts. Here, in the photosynthetic machinery embedded in these membranes phytoplankton can fix carbon dioxide (CO2), with about half of the global carbon fixation occurring in the oceans. But what happens, if the composition of lipid membranes is changed for example due to external stressors such as nutrient limitation? I am presently starting my own lab. My current research focuses on investigating consequences of such lipid remodelling on carbon fixation in the ocean. This will help to better understand potential consequences of climate change and how it will affect cell physiology, thus, improving climate model predictions. Phosphorus (P) limitation is a global challenge to primary production both in terrestrial and marine environments. As an adaptation to low phosphate availability, marine phytoplankton can substitute P-containing lipids for other non-P-containing lipids. This lipid remodelling process provides P for essential cellular functions such as nucleic-acid synthesis. Using liquid chromatography – mass spectrometry I am investigating this lipid remodelling process following P-limitation in laboratory phytoplankton cultures. Monitoring carbon fixation rates of a radiolabelled CO2 source and photophysiological measurements allow to determine consequences associated to lipid remodelling in the P-limited culture in comparison to non-limited controls. Together with other results from investigations targeting cell physiology, findings on carbon fixation rates will be used to improve primary production ecosystem models. Additionally, I am involved in a few collaborations looking at the relevance of lipids. For example, we found that viral infection of an eukaryotic microalga resulted in strong changes of the lipid profile only a few hours after infection. In the coccolithophore Gephyrocapsa (Emiliania) huxleyi I could show the depletion of host-specific sterols originating from the mevalonate-isoprenoid pathway during lytic viral infection (Rosenwasser, Mausz et al., 2014, Plant Cell https://doi.org/10.1105/tpc.114.125641). Further, I looked at lipids in a nematode host and its chemosynthetic symbiont in oxic-anoxic interfaces. Lipid profiles exhibited an increase in the relative abundance of lysophospholipids under anoxia as well as incorporation of host lipids into the symbiont’s membranes (Paredes et al., 2021, mSystems https://doi.org/10.1128/mSystems.01186-20; Paredes et al., 2022, Sci. Rep. https://doi.org/10.1038/s41598-022-13235-9).