Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA.
Archaea. 2012;2012:845756. doi: 10.1155/2012/845756. Epub 2012 Nov 14.
Radiation-resistant bacteria have garnered a great deal of attention from scientists seeking to expose the mechanisms underlying their incredible survival abilities. Recent analyses showed that the resistance to ionizing radiation (IR) in the archaeon Halobacterium salinarum is dependent upon Mn-antioxidant complexes responsible for the scavenging of reactive oxygen species (ROS) generated by radiation. Here we examined the role of the compatible solutes trehalose, mannosylglycerate, and di-myo-inositol phosphate in the radiation resistance of aerobic and anaerobic thermophiles. We found that the IR resistance of the thermophilic bacteria Rubrobacter xylanophilus and Rubrobacter radiotolerans was highly correlated to the accumulation of high intracellular concentration of trehalose in association with Mn, supporting the model of Mn(2+)-dependent ROS scavenging in the aerobes. In contrast, the hyperthermophilic archaea Thermococcus gammatolerans and Pyrococcus furiosus did not contain significant amounts of intracellular Mn, and we found no significant antioxidant activity from mannosylglycerate and di-myo-inositol phosphate in vitro. We therefore propose that the low levels of IR-generated ROS under anaerobic conditions combined with highly constitutively expressed detoxification systems in these anaerobes are key to their radiation resistance and circumvent the need for the accumulation of Mn-antioxidant complexes in the cell.
耐辐射细菌引起了科学家们的极大关注，他们试图揭示这些细菌令人难以置信的生存能力背后的机制。最近的分析表明，古菌盐沼盐杆菌对电离辐射 (IR) 的抗性依赖于 Mn 抗氧化复合物，该复合物负责清除辐射产生的活性氧 (ROS)。在这里，我们研究了相容溶质海藻糖、甘露糖甘油酸盐和二肌醇磷酸在好氧和厌氧嗜热微生物辐射抗性中的作用。我们发现，嗜热细菌木糖杆菌和耐辐射红球菌的 IR 抗性与 Mn 结合的高细胞内海藻糖浓度的积累高度相关，支持了好氧菌中 Mn(2+)-依赖的 ROS 清除模型。相比之下，超嗜热古菌伽马耐受球菌和嗜热球菌 furiosus 中不含有大量的细胞内 Mn，我们也没有发现甘露糖甘油酸盐和二肌醇磷酸在体外有显著的抗氧化活性。因此，我们提出在厌氧条件下产生的低水平的 IR 生成的 ROS 以及这些厌氧菌中高度组成型表达的解毒系统是它们具有辐射抗性的关键，避免了细胞内 Mn 抗氧化复合物的积累。
