Stress resistance of halophilic Archaea from Lunenburg, Germany: implications for astrobiology

Kurzfassung

Here we present the resistance of two halophilic Archaea, Halorubrum (Hrr.) sp. AS12 and Haloarcula (Har.). sp. NS06, isolated from the brine in Lunenburg, Germany, to stress factors including desiccation, radiation and elevated perchlorate concentration. This is the first study to describe the stress resistance of halophilic Archaea isolated from the Lunenburg brine. While Hrr. sp. AS12 tolerates desiccation up to 45 days with a -log3 reduction in survival, Har. sp. NS06 displays a strong decline in viability and no detectable survival following 21 days. In contrast, Hrr. sp. AS12 was more sensitive towards X-Ray irradiation with a significant decline in viability (D₁₀ 228,2 ± 8,9 Gy) while Har. sp. NS06 showed a slight decline in survival following exposure to 1 kGy. The resistance of both strains against germicidal UV-C254nm radiation follows a similar pattern when compared to X-ray exposure with Hrr. sp. AS12 displaying more sensitivity to UV-C radiation (F₁₀ 111,6 ± 6,4 J/m²) compared to Har. sp. NS06 (F₁₀ 194,9 ± 13,7 J/m²). Exposure to He, Ar, and Fe heavy ions up to 500 Gy showed little effect on the survivability; however, the transport control of Hrr. sp. AS12 showed a strong decline (-log3 reduction) in survival. Both strains revealed increased growth in the presence of perchlorates (NaClO₄ and MgClO₄) with a clear preference to NaClO₄ up to 5%. Our results provide a first insight into the stress resistance of these two isolates and will further develop our understanding of the parameters of life on Earth and potentially on other planets.