Dose K, Klein A
Institut für Biochemie, Fachbereich Chemie und Pharmazie, Johannes Gutenberg-Universität, Mainz, Germany.
Orig Life Evol Biosph. 1996 Feb;26(1):47-59. doi: 10.1007/BF01808159.
Spores of Bacillus subtilis have been exposed to the conditions of extreme dehydration (argon/silica gel; simulated space vacuum) for up to 12 weeks at 298 K and 80 K in the dark. The inactivation has been correlated with the production of DNA-double strand-breaks. The temperature-dependence of the rate constants for inactivation or production of DNA-double strand-breaks is surprisingly low. Controls kept in the frozen state at 250 K for the same period of time showed no sign of deterioration. In another series of experiments the spores have been UV irradiated (253.7 nm) at 298 K, 200 K and 80 K after exposure to dehydrating conditions for 3 days. Fluence-effect relationships for inactivation, production of DNA-double strand-breaks and DNA-protein cross-links are presented. The corresponding F37-values for inactivation and production of DNA lesions are significantly increased only at 80 K (factor of 4 to 5). The data indicate that the low temperatures that prevail in the outer parts of the Solar System or at the nightside of Mars or the Moon are not sufficiently low to crucially inhibit inactivation by dehydration. Our data place further constraints on the panspermia hypothesis.
枯草芽孢杆菌的孢子在黑暗中于298 K和80 K下暴露于极端脱水条件（氩气/硅胶；模拟太空真空）长达12周。失活与DNA双链断裂的产生相关。失活或DNA双链断裂产生的速率常数的温度依赖性出奇地低。在250 K下冷冻保存相同时间的对照未显示出降解迹象。在另一系列实验中，孢子在暴露于脱水条件3天后，于298 K、200 K和80 K下进行紫外线照射（253.7 nm）。给出了失活、DNA双链断裂产生和DNA-蛋白质交联的通量-效应关系。仅在80 K时，DNA损伤失活和产生的相应F37值才显著增加（4至5倍）。数据表明，太阳系外部、火星或月球夜侧普遍存在的低温不足以严重抑制脱水导致的失活。我们的数据对泛种论假说施加了进一步限制。
