Functional metatranscriptomics of Antarctic biological soil crust algae: Identification of key genes for the survival under the extreme conditions of Antarctica.

Biocrusts are microbial topsoil communities comprised of phototrophic and heterotrophic organisms, which are embedded together within a matrix of exopolysaccharides and soil particles to yield a surface crust. They are major players in the global biogeochemical cycles of carbon and nitrogen especially in the Polar Regions where vegetation is limited.

In this project, we are interested in phototrophic communities inhabiting polar biocrusts. Compared to aquatic environments, eukaryotic microalgae and cyanobacteria of polar biocrusts are exposed to harsher environmental conditions, such as seasonal and even diurnal fluctuating air temperatures (including frequent freeze/thaw cycles) and regular desiccation as well as high summer insolation. Yet, their physiological responses and acclimation strategies remain uncertain.

In this regard, we will apply high-throughput sequencing of RNA transcripts (metatranscriptomics) to study the biodiversity and structure of dormant and active microorganisms in the polar biocrusts. Metatranscriptomics is able to record expressed transcripts of soil microbial communities at a given point of time under a set of environmental conditions and, thus, to assess functional and taxonomical dynamics of the expressed microbiome.

Furthermore, we will establish new cultures of Klebsormidium and Coccomyxa, isolated from polar biocrusts, and conduct laboratory stress experiments (light, temperature and desiccation). Stress response transcriptomes will be then analysed in order to better understand adaptation mechanisms of biocrust microalgae.

• Desiccation is the major stressor of aero-terrestrial algae in Arctic BSCs in-situ.
• Light and the observed current temperature range play only a minor role as stressors in-situ?
• What effect do higher temperatures have on stress resilience of BSC microalgae?
• Are there specific stress related genes, indicative of the major stressor(s) in situ, which can be used across different species?
• Are there key genes for the survival of terrestrial microalgae in Antarctica?