Life in the Brine of Lunenburg, Germany: Unveiling Microorganisms associated with Zechstein Salt Deposits

Katharina Runzheimer¹Laura Schwab²Denise Engel¹Christoph Schaudinn³Michael Laue³Katarína Rebrošová⁴Kristina Beblo-Vranesevic¹Stefan Leuko^1*

• ¹German Aerospace Center (DLR), Cologne, Germany
• ²Friedrich Schiller University Jena, Jena, Thuringia, Germany
• ³Robert Koch Institute (RKI), Berlin, Berlin, Germany
• ⁴Masaryk University, Brno, South Moravia, Czechia

The presence of hypersaline brines on other planets and moons in the inner and outer solar system has been well established. Hence, one theory of life existing on other planets would need the microorganisms to be adapted to high salt concentrations. The hypersaline brine from Lunenburg (Germany) with 302.25 g L-1 NaCl, originating from the remnants of the Zechstein ocean, has long been utilized to harvest salt, but potential microbial life in the brine has never been investigated. Our research shows, that the brine from Lunenburg harbors a diverse microbial community and is an ideal and easily accessible testbed to search for novel microorganisms to use for astrobiological studies. We employed cultivation-based and -independent methods to characterize the microbial diversity, while also analyzing environmental parameters. Our findings proved a broad range of extremely halophilic microorganisms, including sulfate-reducing bacteria, haloarchaea and yet-uncultivated microorganisms like Nanohaloarchaeota and Patescibacteria. Two haloarchaeal isolates are described in more detail, revealing the presence of bacterioruberin for oxidative stress protection, potential polyhydroxyalkanoates for energy storage, and pleomorphic structures as well as "package-like aggregates" as possible adaptations to extreme conditions. Distinct osmotic adaptation strategies and a low average isoelectric point of the isolates proteomes were identified.