Université Paris-Sud 11, UMR-CNRS 8621, Institut de Génétique et de Microbiologie, Laboratoire de Génomique des Archaea, Orsay, France.
PLoS One. 2012;7(7):e41935. doi: 10.1371/journal.pone.0041935. Epub 2012 Jul 27.
Thermococcus gammatolerans, the most radioresistant archaeon known to date, is an anaerobic and hyperthermophilic sulfur-reducing organism living in deep-sea hydrothermal vents. Knowledge of mechanisms underlying archaeal metal tolerance in such metal-rich ecosystem is still poorly documented. We showed that T. gammatolerans exhibits high resistance to cadmium (Cd), cobalt (Co) and zinc (Zn), a weaker tolerance to nickel (Ni), copper (Cu) and arsenate (AsO(4)) and that cells exposed to 1 mM Cd exhibit a cellular Cd concentration of 67 µM. A time-dependent transcriptomic analysis using microarrays was performed at a non-toxic (100 µM) and a toxic (1 mM) Cd dose. The reliability of microarray data was strengthened by real time RT-PCR validations. Altogether, 114 Cd responsive genes were revealed and a substantial subset of genes is related to metal homeostasis, drug detoxification, re-oxidization of cofactors and ATP production. This first genome-wide expression profiling study of archaeal cells challenged with Cd showed that T. gammatolerans withstands induced stress through pathways observed in both prokaryotes and eukaryotes but also through new and original strategies. T. gammatolerans cells challenged with 1 mM Cd basically promote: 1) the induction of several transporter/permease encoding genes, probably to detoxify the cell; 2) the upregulation of Fe transporters encoding genes to likely compensate Cd damages in iron-containing proteins; 3) the induction of membrane-bound hydrogenase (Mbh) and membrane-bound hydrogenlyase (Mhy2) subunits encoding genes involved in recycling reduced cofactors and/or in proton translocation for energy production. By contrast to other organisms, redox homeostasis genes appear constitutively expressed and only a few genes encoding DNA repair proteins are regulated. We compared the expression of 27 Cd responsive genes in other stress conditions (Zn, Ni, heat shock, γ-rays), and showed that the Cd transcriptional pattern is comparable to other metal stress transcriptional responses (Cd, Zn, Ni) but not to a general stress response.
嗜热古菌伽马耐受菌是迄今为止已知的最具放射性抗性的古菌，是一种生活在深海热液喷口的厌氧和高温嗜硫微生物。在如此富含金属的生态系统中，有关古菌金属耐受性机制的知识仍鲜有记载。我们表明，T. gammatolerans 对镉 (Cd)、钴 (Co) 和锌 (Zn) 表现出高抗性，对镍 (Ni)、铜 (Cu) 和砷酸盐 (AsO(4)) 的耐受性较弱，并且暴露于 1mM Cd 的细胞表现出 67µM 的细胞内 Cd 浓度。使用微阵列进行了时间依赖性转录组分析，在非毒性 (100µM) 和毒性 (1mM) Cd 剂量下进行。通过实时 RT-PCR 验证增强了微阵列数据的可靠性。总共揭示了 114 个 Cd 响应基因，其中很大一部分基因与金属稳态、药物解毒、辅因子再氧化和 ATP 产生有关。这是对 Cd 挑战的古菌细胞进行的全基因组表达谱研究首次表明，T. gammatolerans 通过在原核生物和真核生物中观察到的途径以及通过新的和原始的策略来承受诱导的应激。用 1mM Cd 处理的 T. gammatolerans 细胞基本上促进：1）几种转运蛋白/渗透酶编码基因的诱导，可能是为了解毒细胞；2）铁转运蛋白编码基因的上调，以可能补偿含铁蛋白中的 Cd 损伤；3）膜结合氢化酶 (Mbh) 和膜结合氢化酶 (Mhy2) 亚基编码基因的诱导，这些基因参与还原辅因子的再循环和/或质子转运以产生能量。与其他生物体不同，氧化还原稳态基因似乎是组成型表达的，只有少数编码 DNA 修复蛋白的基因受到调控。我们比较了 27 个 Cd 响应基因在其他应激条件（Zn、Ni、热休克、γ 射线）下的表达情况，并表明 Cd 转录模式与其他金属应激转录反应（Cd、Zn、Ni）相似，但与一般应激反应不同。
