MICINSNOW - Microbial Interactions in Snow-Covered Habitats

Snow-covered landscapes suggest an image of dormancy and hibernation. However, underneath the snow cover soil is teeming with microbial activity. The project MICINSNOW - Microbial Interactions in Snow Covered Habitats investigates interactions of soil microbial communities (MCs) depending on the season. MCs are investigated at three different habitat types, ranging from recently de-glaciated bare terrain in the glacier forefield, over alpine dwarf shrub communities with about 150 years of soil development, to a Swiss stone pine forest with a distinct humus layer. The hypotheses to test are: 1) Snow-covered soil harbours typical winter MCs. 2) There are typical associations between winter-active fungi and prokaryotic microorganisms (bacteria, archaea),which co-occurdueto mutual dependencies. 3) Fungi dominate winter-active MCs and a large proportion of them are currently unknown. To test these hypotheses, the total of microbial organisms is captured by massive parallel sequencing of soil DNA and RNA, which enables us to simultaneously get information about the identity and activity of the present soil microorganisms. Bioinformatics and statistical analyses deliver first conclusions on microbial interactions, which will be tested in a second step by visual methods (FISH: fluorescence in situ hybridization). To selectively isolate winter-active fungi by a cultivation-dependent approach, in-growth mesh bags filled with sterile quartz sand are buried in the soil. Fungi that are active during the time of burial will grow through the bags and leave biomass on the quartz sand. Fungal isolates can then be obtained by incubation of sand grains on nutrient media. Pure cultures are classified based on morphological characteristics and unambiguously identified by marker genes. Previouslyunknownisolates are characterizedwithcomparativemorphological, physiological, and phylogenetic methods and described as new species. All isolates will be deposited in public microbial culture collections and thus made available to the scientific community for further studies (e.g. screening for cold-adapted enzymes). What makes this project particularly innovative and valuable is that interactions of active soil MCs are investigated based a combination of cultivation, culture-independent molecular methods, visual methods and modern bioinformatics tools. The knowledge on typical interactions between microorganisms provides insights in the potential role of microbial associations in cold soil, and sets the stage for further experimental studies on the function of fungi and prokaryotic organisms in snow-covered soils.

Soil is populated by a high diversity of both fungi and bacteria. Alone and in collaboration in microbial interaction, these microorganisms are involved in nutrient cycling and soil development. Soil microbial communities are affected by changes in environmental conditions. They are not dormant during winter, because the insulating snowpack protects microorganisms from frost damage. Until now, however, the seasonality effect on microbial communities has poorly been studied. Therefore, our understanding of soil nutrient cycling is very incomplete. Especially in (sub-)alpine regions, where snow-cover periodically and drastically changes environmental conditions, knowledge is missing. Increased understanding, however, is necessary to predict future ecosystem developments, especially given global warming. Moreover, (sub-)alpine ecosystems still harbour a high number of undiscovered species, especially cold-adapted ones, which need to be described before their possible disappearance due to the effects of global warming. The project MICINSNOW aimed at (i) identifying and (ii) isolating co-occurring fungi and bacteria actively growing in snow-covered (sub-)alpine soil and (iii) detecting their sensitivity to environmental conditions. To achieve these aims, we collected soil samples from (sub-)alpine forests across the Austrian Alps and from glacier forefields in Austria, Italy, and Switzerland, and we analysed them using classical microbiological isolation techniques and molecular biological methods. We found that both fungal and bacterial communities and their associations differed depending on snow-cover. Both, microbial communities and their associations, depended on environmental conditions. For these reasons, they are likely subject to climate change, which might affect soil nutrient cycling and development. Across all (sub-)alpine locations studied, we frequently detected Mortierellaceae as abundant fungus. These ubiquitious soil fungi drive soil development by growing in nutrient-poor soils and they promote plant growth, amongst others by recruiting beneficial bacteria. Studying these ecosystems, we discovered and described more than a dozen new species belonging to this family of soil fungi, thereby adding fundamental knowledge to the tree of life and contributing to biodiversity conservation. As hypothesized, we also found several typical associations between Mortierellaceae and bacteria. Researching their means of association, based on our results, we hypothesize that they might communicate using both volatile and soluble compounds, which might have application in both plant growth promotion and ecosystem management. Overall, the MICINSNOW project published more than 10 scientific publications in high ranked journals, presented its results on numerous international conferences with a broad audience, contributed to social and academic education and future research on global scale, and strengthened the international position of the Universität Innsbruck as centre of excellence in alpine research and fungal systematics. The project also promoted fungal systematics as fascinating, relevant and cutting-edge field of research that is worth further research.