The extremophilic bacterium Deinococcus radiodurans displays an extraordinary ability to withstand lethal radiation effects, due to its complex mechanisms for both proteome radiation protection and DNA repair. Published results obtained recently at this laboratory show that D. radiodurans submitted to ionizing radiation results in its DNA being shattered into small fragments which, when exposed to a "static electric field' (SEF), greatly decreases cell viability. These findings motivated the performing of D. radiodurans exposed to gamma radiation, yet exposed to a different exogenous physical agent, "static magnetic fields" (SMF). Cells of D. radiodurans [strain D.r. GY 9613 (R1)] in the exponential phase were submitted to 60Co gamma radiation from a gamma cell. Samples were exposed to doses in the interval 0.5-12.5 kGy, while the control samples were kept next to the irradiation setup. Exposures to SMF were carried out with intensities of 0.08 T and 0.8 T delivered by two settings: (a) a device built up at this laboratory with niobium magnets, delivering 0.08 T, and (b) an electromagnet (Walker Scientific) generating static magnetic fields with intensities from 0.1 to 0.8 T. All samples were placed in a bacteriological incubator at 30 °C for 48 h, and after incubation, a counting of colony forming units was performed. Two sets of cell surviving data were measured, each in triplicate, obtained in independent experiments. A remarkable similarity between the two data sets is revealed, underscoring reproducibility within the 5% range. Appraisal of raw data shows that exposure of irradiated cells to SMF substantially increases their viability. Data interpretation strongly suggests that the increase of D. radiodurans cell viability is a sole magnetic physical effect, driven by a stochastic process, improving the efficiency of the rejoining of DNA fragments, thus increasing cell viability. A type of cut-off dose is identified at 10 kGy, above which the irradiated cellular system loses recovery and the cell survival mechanism collapses.

中文翻译：

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耐辐射奇异球菌暴露于静磁场和伽马辐射：观察细胞恢复效果

由于其复杂的蛋白质组辐射保护和 DNA 修复机制，极端嗜热细菌耐辐射奇异球菌表现出非凡的抵御致命辐射效应的能力。最近在该实验室获得的已发表结果表明，D. radiodurans 受到电离辐射导致其 DNA 被粉碎成小碎片，当暴露于“静电场”（SEF）时，会大大降低细胞活力。这些发现激发了执行D. radiodurans 暴露于伽马辐射，但暴露于不同的外源物理因子，“静磁场”（SMF）。处于指数相的 D. radiodurans [菌株 Dr GY 9613 (R1)] 被提交给 60Co γ来自伽马细胞的辐射。样品暴露于 0.5-12.5 kGy 的剂量范围内，而对照样品则放在辐照装置旁边。暴露于 SMF 的强度为 0.08 T 和 0.8 T，通过两种设置提供：(a) 在该实验室构建的带有铌磁铁的设备，提供 0.08 T，和 (b) 产生静磁场的电磁体 (Walker Scientific)强度为 0.1 至 0.8 T 的场。所有样品置于 30 °C 的细菌培养箱中 48 小时，培养后，进行菌落形成单位的计数。测量两组细胞存活数据，每组一式三份，在独立实验中获得。揭示了两个数据集之间的显着相似性，强调了 5% 范围内的再现性。对原始数据的评估表明，将受辐照的细胞暴露于 SMF 会显着提高其生存能力。数据解释有力地表明，耐放射虫细胞活力的增加是唯一的磁物理效应，由随机过程驱动，提高了 DNA 片段重新连接的效率，从而提高了细胞活力。一种类型的截止剂量被确定为 10 kGy，超过该剂量，受照射的细胞系统将失去恢复能力，细胞存活机制崩溃。