From single pioneers to complex communities: Simultaneous discrimination of composition and inferring species interactions of fossil as well as modern pro- and eukaryotic microbial communities
Final Report Abstract
The following four hypotheses were formulated and tested as far as possible within the framework of the project: H1: Prokaryotic microorganisms are the key players for the initial development of soil environments in Antarctica. They are the pioneers for carbon and nitrogen fixation. H2: After colonization begun, an extensive network of different prokaryotic and eukaryotic microorganisms established. They are responsible, on basis of different functions within the network, for the further development of stable soil environments. H3. Desiccation tolerant eukaryotic algae are among the early pioneers of colonization following prokaryotes provided the bioavailability of nitrogen sources (e.g. through heterotrophic bacteria). Eukaryotic algae, as an important part of Antarctica’s terrestrial microbiota, influence diversity and abundances of bacteria and fungi in the non-vegetated soils of ice-free oases of Antarctica H4: Extreme terrestrial environments are colonized by a large number of so far unknown species. They represent an important taxonomic reference base and a valuable genetic source for potential biotechnological applications. The hypotheses could be largely confirmed and the results summarized as follows: • Bacterial and eukaryal communities differ not only between the different plots and within their depth profile but also in their fossil and recent species assembly. • Phototrophs act as carbon-fixing pioneers found in all sites, with Cyanobacteria in higher abundance only closest to the glacier while eukaryotic algae occur in every site. Bryophytes (Grimmia sp.) grow only farthest from the glacier. • Eukaryotic algae show a succession along the chronosequence: Members of green algal class Trebouxiophyceae are highly diverse and are among the first recent colonizers close to the glacier while Stramenopile algae (Xanthophyceae) are present only next to the glacier but persisting in the fossil pool in sites further away from the glacier. • Autotrophic bacteria capable of using trace gases (CO, CH4, H2) for energy and carbon metabolism (WPS-2, methanotrophs) or that are still lacking in knowledge about their functional repertoire (e.g. clades of Chloroflexi, Gemmatimonadetes and Patescibacteria) are prevalent. • Nitrogen-fixing prokaryotes show a high relative abundance, indicating the potential transfer of nitrogen to prokaryotes and eukaryotes. • Many groups of bacteria are known from hot deserts such as the Atacama. These organisms are adapted to extreme environmental conditions such as UV and high salt content (Chloroflexi, some Proteobactera, Gemmatimonadetes), which are also relevant in Antarctic soils of the Larsemann Hills. Actinobacteria are first colonizers and active metabolite producers and therefore play an important role in the development of initial habitats and the biochemical cycles.
