Abiotic stress in extremophiles - strategies and utilization

The term extremophile describes an organism that exists under extreme physical or geochemical conditions, which usually do not permit survival. In alpine regions such habitats are found on exposed rocky surfaces at high altitude, where several stress factors like increased UV-VIS radiation, vast temperature differences or a limited water and nutrient supply create a hostile environment. Yet, a few specialized organisms like green algae and cyanobacteria are able to survive. Despite these highly relevant ecological aspects little is known about the respective organisms. Most of them were identified taxonomically, but data about their secondary metabolites, their bioactivity or defence mechanisms in response to external stress is missing. Our project will overcome this lack of information by, for the first time, systematically studying changes in the metabolic patterns of alpine high altitude green algae and cyanobacteria exposed to elevated UVA and UVB radiation. Special focus will be put not only on the identification of respective compounds, but also on the fact whether these metabolites show bioactivity as well (anti-inflammatory, skin protection). Initially, from a selection of eleven different green algae and cyanobacteria the two pharmacologically most active ones will be selected after exposure of the specimens. They will be cultivated in larger scale, so that suitable analytical procedures for monitoring UV-stress induced compounds can be developed and bioactive constituents identified by chromatographic and spectroscopic methods. With references at hand further in-depth investigations will follow, targeting questions like when these protective agents are formed (sun simulation experiments) and how their bioactivity can be explained mechanistically (pharmacological studies). Our study joins aspects of ecology with phytochemistry, analytical sciences and pharmacology in a unique way. By investigating metabolites of organisms that hardly have been screened their relation can be studied on a chemosystematic level, their mechanisms of UV-protection investigated, and novel natural products with promising bioactivities explored. This will create a stable foundation for further research on alpine extremophil microorganisms, a group that largely has been overlooked by science till date.

Extremophiles are organisms that are able to survive under hostile environmental conditions like high temperatures or extreme levels of UV irradiation. In course of this research project we mainly focused on extremophilic (high altitude) algae and their strategies of UV-protection. The project followed a multidisciplinary concept, because for its successful realization biological, pharmaceutical, chemical and medicinal aspects were relevant. Accordingly, at the beginning of our studies more than 20 extremophilic algae were selected, cultivated as pure strains, and evaluated for their antioxidative potential. The most active representatives were then submitted to irradiation experiments under controlled conditions, in order to determine which metabolites are increasingly produced in response to UV-stress. It could be shown that not only the synthesis of pigments is stimulated but also the levels of aromatic amino acids, nucleic bases and nucleotides increase. The latter was described for the first time in algae, an observation which is definitely of great ecologic relevance.Another focus of our investigations was the group of mycosporine-like amino acids (MAAs), UV-protecting natural compounds commonly found in algae. We were able to isolate two novel representatives (prasiolin from Prasiola calophylla and catenelline from Catenella repens), and could significantly improve the protocols for MAA purification and analysis. With the currently available methods the latter is not fully satisfying, so that the described separations by hydrophilic interaction chromatography (HILIC) or capillary electrophoresis are highly interesting alternatives. In the course of pharmacological studies some of the MAAs revealed an inhibition of collagenase. This enzyme plays an important role in skin ageing, indicating that the respective compounds might also be interesting for the development of cosmetic products.We tried to investigate the challenging tasks of this project from a wide perspective, which required, apart from creativity and endurance, the establishment and use of diverse techniques and approaches. All this resulted in four already published scientific papers, summarizing an array of new data and perspectives within a research area that has widely been neglected in the past.