Ionizing radiation is one of the main factors limiting the survival of microorganisms in extraterrestrial conditions. The survivability of microorganisms under irradiation depends significantly on the conditions, in which the irradiation occurs. In particular, temperature, pressure, oxygen and water concentrations are of great influence. However, the influence of factors such as the radiation intensity (in low-temperature conditions) and the type of mineral matrix, in which microorganisms are located, has been practically unstudied. It has been shown that the radioresistance of bacteria can increase after their exposure to sublethal doses and subsequent repair of damage under favorable conditions, however, such studies are also few and the influence of other factors of extraterrestrial space (temperature, pressure) was not studied in them. The viability of bacteria Arthrobacter polychromogenes, Kocuria rosea and Xanthomonas sp. after irradiation with gamma radiation at a dose of 1 kGy under conditions of low pressure (1 Torr) and low temperature (−50 °C) at different radiation intensities (4 vs. 0.8 kGy/h) with immobilization of bacteria on various mineral matrices (montmorillonite vs. analogue of lunar dust) has been studied. Native, previously non-irradiated strains, and strains that were previously irradiated with gamma radiation and subjected to 10 passages of cultivation on solid media were irradiated. The number of survived cells was determined by culturing on a solid medium. It has been shown that the radioresistance of bacteria depends significantly on the type of mineral matrix, on which they are immobilized, wherein montmorillonite contributes to an increased survivability in comparison with a silicate matrix. Survivability of the studied bacteria was found to increase with decreasing radiation intensity, despite the impossibility of active reparation processes under experimental conditions. Considering the low intensity of radiation on various space objects in comparison with radiobiological experiments, this suggests a longer preservation of the viable microorganisms outside the Earth than is commonly believed. An increase in bacterial radioresistance was revealed even after one cycle of irradiation of the strains and their subsequent cultivation under favourable conditions. This indicates the possibility of hypothetical microorganisms on Mars increasing their radioresistance.

中文翻译：

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低温条件下辐射强度、矿物基质和预辐照对细菌对伽马辐照耐受性的影响


电离辐射是限制微生物在地外条件下生存的主要因素之一。微生物在辐照下的生存能力很大程度上取决于辐照发生的条件。特别是温度、压力、氧气和水浓度影响很大。然而，辐射强度（低温条件下）和微生物所在的矿物基质类型等因素的影响实际上尚未被研究。研究表明，细菌在接触亚致死剂量后，其辐射抗性会增强，并在有利的条件下修复损伤，但此类研究也很少，并且没有研究外太空其他因素（温度、压力）的影响。在他们之中。细菌多色节杆菌、 Kocuria Rosea和黄单胞菌的活力。在低压（1 Torr）和低温（−50 °C）条件下，以不同辐射强度（4 vs. 0.8 kGy/h）用 1 kGy 剂量的伽马辐射照射后，将细菌固定在各种矿物基质上（蒙脱石与月球尘埃的类似物）已经进行了研究。对天然的、先前未照射的菌株和先前用伽马辐射照射并在固体培养基上培养10次的菌株进行照射。通过在固体培养基上培养来测定存活细胞的数量。 已经表明，细菌的辐射抗性显着取决于细菌所固定的矿物基质的类型，其中与硅酸盐基质相比，蒙脱石有助于提高存活率。尽管在实验条件下不可能进行主动修复过程，但发现所研究的细菌的存活率随着辐射强度的降低而增加。考虑到与放射生物学实验相比，各种空间物体的辐射强度较低，这表明地球以外的存活微生物的保存时间比通常认为的要长。即使在对菌株进行一个周期的照射及其随后在有利条件下的培养之后，也发现细菌的放射抗性有所增加。这表明火星上假设的微生物有可能增加其辐射抗性。