Ecology and Evolution of Archaea, Environmental Genomics

Archaea emerged as a lineage independently from Bacteria about 4 billion years ago on Earth. Although they are mostly known and studied from extreme environments, archaea also play important roles in biogeochemical cycles of moderate ecosystems, such as oceans, lakes, sediments and soils. In addition, their role in the early evolution of the first complex life forms is undebated and receives a lot of attention due to recent findings of novel archaeal lineages. In this project, two groups of archaea that play important ecological and/or evolutionary roles will be studied, ammonia oxidizing archaea and Asgardarchaea. Ammonia oxidizing archaea were discovered in aquatic and terrestrial environments and are together with certain lineages of bacteria responsible for the conversion of nitrogen compounds by oxidizing ammonia to nitrite. Their activity directly and indirectly influences the availability of nutrients to plants and can fuel the production of the strong greenhouse gas nitrous oxide from soil. Nitrososphaera viennensis, an ammonia oxidizing archaeon from soil isolated in Vienna will serve as the model organism to study the physiology and biochemistry of ammonia oxidizing archaea. In particular its metabolic capabilities beyond aerobic ammonia oxidation will be explored as well as particular proteins that we assume have emerged in ammonia oxidizers to enable them to radiate into many moderate aerobic environments on earth. The second archaeal group are Asgardarchaea, that were only discovered in 2015 as the closest known microbial sister lineage of complex organisms, i.e. of all plants, animals and fungi (collectively termed eukaryotes). Asgardarchaea contain hundreds of proteins so far only known in eukaryotes and thus give clues about the evolution of the last eukaryotic common ancestor. Candidatus Lokiarchaeum ossiferum, recently cultivated from anoxic marine sediments by our group will serve as a new model organism. The characterization of its cellular components in particular its dynamic cytoskeleton and the ability for vesicle transport and membrane remodeling will reveal the extent to which features are shared with eukaryotes. This will shed light on the evolutionary emergence of complex life forms from simpler microorganisms. The project will also involve ecological aspects by studying the environmental distribution of both, ammonia oxidizing archaea and Asgardarchaea in terrestrial environments and sediments and by attempting to bring further model organisms into laboratory cultures.