Abstract

Ionizing radiation is an important environmental factor affecting the dynamics of biospheric processes in the past and present, as well as limiting the spread of life outside the Earth. The effect of radiation on microorganisms has been studied for decades, but studies of the response of natural microbial ecosystems are still scarce. We have studied the effect of 100 kGy gamma irradiation under low pressure (1 Torr) and low temperature (–50°C) on microbial community of the ancient Antarctic permafrost sedimentary rock. After irradiation, the total number of prokaryotic cells determined by epifluorescence microscopy, as well as the number of metabolically active bacterial and archaeal cells detected by fluorescence in situ hybridization remained at the control level, while the number of cultured heterotrophic bacteria decreased by an order of magnitude. Using the multisubstrate testing method, it has been found that the microbial complex retained a high potential metabolic activity and functional diversity after exposure to a combination of extreme physical factors. The resistance demonstrated by the microbial community significantly exceeded the generally accepted estimates of the prokaryotes’ radioresistance and indicated an underestimation of the microorganisms' radioresistance in natural habitats and the important role of mineral heterophase environment and irradiation conditions (pressure, temperature). The study confirmed the potential for long-term cryopreservation of viable terrestrial-like microorganisms in the Martian regolith, as well as the possibility of transferring anabiotic life forms as a part of small bodies in the space environment.

中文翻译：

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模拟火星条件下伽玛射线辐照后古南极多年冻土的原核群落

摘要

电离辐射是影响过去和现在生物圈过程动力学的重要环境因素，并限制了生命在地球外部的传播。辐射对微生物的影响已进行了数十年的研究，但对自然微生物生态系统响应的研究仍然很少。我们研究了在低压（1 Torr）和低温（–50°C）下100 kGy伽马射线辐照对古代南极多年冻土沉积岩微生物群落的影响。辐照后，通过落射荧光显微镜确定的原核细胞总数以及通过荧光原位杂交检测的代谢活性细菌和古细菌细胞的数量保持在对照水平，培养的异养细菌数量减少了一个数量级。使用多底物测试方法，发现微生物复合物在暴露于极端物理因素的组合后仍保留了高潜在的代谢活性和功能多样性。微生物群落所表现出的抗性大大超出了原核生物抗辐射性的普遍接受的估计值，并表明低估了微生物在自然栖息地中的抗辐射性以及矿物异相环境和辐照条件（压力，温度）的重要作用。这项研究证实了在火星长石中长期低温保存可行的陆地样微生物的潜力，