Cultivation of high-altitude lakes in Atacama Desert as extraterrestrial analogous habitats for astrobiological research

Kurzfassung

Background: Out of up to one trillion (10¹²) microbial species only 10⁴ species have been cultured and less than 10⁵ species are well presented by categorized sequences [1]. According to this numbers, 99.999 % of microbial taxa remain undiscovered [1] which indicates an enormous knowledge gap in the genetic repertoire for diverse biotechnological applications. Especially extreme habitats which are hard to access are poorly microbial investigated. A special interest from astrobiologists is layed on the research of extreme extraterrestrial analogous habitats. An example are the highest lakes on Earth, located in the Andes in south America, which are classified as model systems for extraterrestrial life [2]. They are characterized by low oxygen, high UV-radiation, and chemical extremes like high dissolved salt contents including high arsenic salts with up to 234 ppm as well as alkalinity [3]. Extremophilic organisms often exhibit resistance genes, such as for pigmentation, which can protect against radiation, cold or other stress factors. Microbial pigments therefore offer a wide range of biotechnological uses such as radiation protection in space missions or as food additives and medical products like vitamin precursors. The goal of this study is to describe yet unwell described extraterrestrial habitats and access the microbial life here to extend the list of previously uncultivated organisms and expand the genetic knowledge. Material and Methods: In this work five different high-altitude lakes from Atacama Desert were analyzed and identified according to cultivable organisms. First of all, chemical analysis of salt, pH, temperature and UV irradiation was measured and revealed partly high salt concentration of up to 27 % and alkaline pH in some places. Cultivation was performed by using standard media for aquatic ecosystems (R2A and Marine Broth) and was complemented by individual environmental-close cultivation. Results show that especially modifying the pH according to the initial environmental conditions results in higher cultivability. To select especially astrobiology-relevant isolates, cultivation was also performed after stress treatment with X-rays. Over 100 different isolates were generated and will be identified via 16S rRNA Sequencing. Besides single species characterization, the overall cultivation strategies will contribute to the recently BMBF founded project “MultiKulti”. The vision of this project is to develop a bioreactor system that simulates habitat conditions as closely as possible for systematic isolation experiments of target- and yet uncultivated organisms in the long term.