Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are membrane-spanning lipids occurring in the cell membrane of bacteria. These lipids are widely distributed in various environmental systems, whereby their distribution depends on temperature and pH. In addition, brGDGTs are used for the reconstruction of past terrestrial temperatures. My research focuses on the investigation of the biosynthesis pathways of brGDGTs as well as their role in the bacterial cell membrane because they are still unknown.