Research

1. Physiology of anaerobic Microorganisms
   
   Bacteria and archaea have already been shaping Earth’s biogeochemistry for billions of years, colonizing almost all known environments and playing a critical role in the biogeochemical cycling of key elements such as carbon, as well as for Earth’s climate. We are particularly interested in studying anaerobic bacteria and archaea, which are adapted to life without oxygen. Archaea are procaryotes that form one of the domains of life alongside bacteria, and can partly thrive in extreme environments such as hydrothermal vents or hot springs. In recent years, many new archaeal lineages have been discovered by modern high-throughput sequencing methods, but their isolation and physiological characterization lag far behind. By physiological and biochemical characterizations of yet uncharacterized bacterial and archaeal metabolic pathways and the enzymes involved, we aim to increase our knowledge of archaeal and bacterial physiology and contribute to assigning functions to the large number of uncharacterized archaeal and bacterial genes. 
    
2. Investigating methoxydotrophic Archaea & Bacteria
   
   Methoxylated aromatic compounds are key components of lignin and coal and are very abundant on Earth. Bacterial growth on methoxylated aromatics has been known for decades. The conversion of methoxylated aromatics is catalyzed by corrinoid-dependent methyltransferase systems. Although these systems are widespread in anaerobic bacteria, only a few have been characterized to date. In contrast to bacteria, archaea have only recently been shown to have the ability to convert methoxylated aromatics using similar enzyme systems [1, 2, 3]. Archaea convert methoxylated aromatics to the greenhouse gases methane and/or CO2. To gain a deeper insight into the microbial conversion of methoxylated aromatics and the environmental role of methoxydrotrophic archaea and bacteria, we aim to characterize various archaeal and bacterial O-demethylase systems, to study the metabolism in detail and to investigate the ecophysiology of these microorganisms.
   
   [1] Mayumi et al. (2016) Science 354: 222-225
   [2] Kurth et al. (2021) ISME J 15: 3549–3565
   [3] Welte (2021) Environ Microbiol 23: 4017-4033
3. Unraveling novel Archaeal Metabolic Pathways impacting Greenhouse Gas Emissions (ERC Starting Grant project ARCHAEBOLIC)
   
   Methanogenic archaea are the main producers of the greenhouse gas methane. Especially in view of climate change, it is crucial to understand all factors impacting greenhouse gas emissions. In previous work (Kurth et al. (2021) ISME J) we identified and characterized a novel enzyme system enabling (methanogenic) archaea to convert wood components, so-called methoxylated aromatics. The novel enzyme systems involved are widespread and new metabolic pathways involving a variety of methylated substrates can be predicted, suggesting an important role of archaea in anaerobic conversions of lignin and various methylated compounds to methane and/or CO2. Therefore, we aim to (i) characterize these novel enzyme systems biochemically and in regard to their evolution, (ii) study the physiology of the archaea using these systems and (iii) evaluate the role of these archaea in the environment and for methane and CO2 emissions. Identifying new archaeal substrates involved in methane and CO2 production enables us to assess the impact of these conversions on the environment and global methane and CO2 budgets.