Salt City Secrets: Astrobiological Exploration of Lüneburg's Halophilic Microorganisms

Abstract

Introduction: Extreme saline habitats, distinguished by elevated concentrations of salt, have emerged as captivating hotspots for astrobiological exploration. Despite being commonly perceived as harsh and inhospitable, these environments play host to a range of extremophiles. One such extreme habitat is the Lüneburger brine, characterized by a saturated saline solution that surpasses all other European brines in terms of salinity. Historically utilized as a source of salt, this brine offers easy accessibility for sampling campaigns. The significance of extremophiles isolated from saline environments lies in their potential to provide crucial insights into the boundaries of life on Earth and, by extension, the prospect of extraterrestrial life. Goals: The study aims to characterize the Lüneburger brine in Germany. Cultivation and cultivation independents methods will be used to further investigate the extreme microbial community and to evaluate if this brine represents an astrobiological relevant habitat. Material and Methods: In this study, we conducted extensive sampling of the Lüneburger brine. Analyses encompassed the metagenome, the cultivable community, and the chemical compositions of the brine itself. Selected isolates were further tested on potential resistances to astrobiological relevant stressors like radiation. Results: Metagenomic data unveiled the presence of halophilic Archaea, showcasing thermophilic, halophilic, and acidophilic characteristics. Several representatives were identified as candidate organisms, yet to be isolated in a pure culture. Microscopic analysis indicated potential variations in morphology, with the isolates displaying pleomorphism. The majority of cultivated organisms exhibited the presence of the carotenoid bacterioruberin. Future experiments will assess the resistance of these isolates to common astrobiological stressors, including radiation, salt, and perchlorate tolerance. Summary: The Lüneburger Brine displays an extreme habitat displaying a saturated saline solution. However, our study has shown the wide diversity of especially halophilic microorganism which thrive in this habitat. The study emphasis the potential of this easily accessible habitat for current astrobiology research and shows the presence of isolates capable of diverse resistance towards high salinity, radiation and more revealing pleomorph structures and pigmentation.