Polyphosphates (PolyP) are linear polymers of orthophosphate residues that have been proposed to participate in metal resistance in bacteria and archaea. In addition of having a CopA/CopB copper efflux system, the thermoacidophilic archaeon Metallosphaera sedula contains electron-dense PolyP-like granules and a putative exopolyphosphatase (PPX_Msed, Msed_0891) and four presumed pho84-like phosphate transporters (Msed_0846, Msed_0866, Msed_1094, and Msed_1512) encoded in its genome. In the present report, the existence of a possible PolyP-based copper-resistance mechanism in M. sedula DSM 5348^T was evaluated. M. sedula DSM 5348^T accumulated high levels of phosphorous in the form of granules, and its growth was affected in the presence of 16 mM copper. PolyP levels were highly reduced after the archaeon was subjected to an 8 mM CuSO₄ shift. PPX_Msed was purified, and the enzyme was found to hydrolyze PolyP in vitro. Essential residues for catalysis of PPX_Msed were E111 and E113 as shown by a site-directed mutagenesis of the implied residues. Furthermore, M. sedula ppx, pho84-like, and copTMA genes were upregulated upon copper exposure, as determined by qRT-PCR analysis. The results obtained support the existence of a PolyP-dependent copper-resistance system that may be of great importance in the adaptation of this thermoacidophilic archaeon to its harsh environment.

中文翻译：

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球形小球藻DSM 5348T中的无机多磷酸盐，外多磷酸酶和类似Pho84的转运蛋白可能与铜抗性有关。

聚磷酸盐（PolyP）是正磷酸盐残基的线性聚合物，已提出参与细菌和古细菌的金属抗性。除了具有CopA / CopB铜外排系统外，嗜热古生金属小球藻中还包含电子致密的PolyP样颗粒和推定的胞外多磷酸酶（PPX _Msed，Msed_0891）和四个推测的pho84样磷酸盐转运蛋白（Msed_0846，Msed_0866，Meded_0866，Msed_0866，和Msed_1512）编码在其基因组中。在本报告中，S。sedula DSM 5348 ^T中存在基于PolyP的铜抗性机制被评估。s。sedula DSM 5348 ^T以颗粒形式积聚高水平的磷，在16 mM铜的存在下其生长受到影响。在将古细菌进行8 mM CuSO ₄转移后，PolyP水平大大降低。纯化PPX _Msed，发现该酶可在体外水解PolyP 。如隐含位点的定点诱变所示，催化PPX _Msed的基本残基为E111和E113。此外，还有M. sedula ppx，pho84样和copTMA通过qRT-PCR分析确定，铜暴露后基因上调。获得的结果支持存在依赖于PolyP的铜抗性系统，这可能对于使这种嗜热古细菌适应其恶劣环境具有重要意义。