Bioleaching, an alternative environmental smelting technology, typically uses high concentrations of heavy metal ions, especially in the subsequent phase, due to metal ion accumulation from the mineral. In this study, we analyzed the overall response of the bioleaching microorganism Acidithiobacillus caldus to copper stress through physiological and transcriptomic analyses. Scanning electron microscopy results showed higher extracellular polymeric substances secretion and cell aggregation under copper stress. Intracellular levels of glutamic acid, glycine and cysteine increased, favoring the synthesis of glutathione for maintenance of the oxidation-reduction state. GSH, during copper stress conditions, the activity of GSH-PX and CAT increased, resulting in reduced oxidative damage while maintaining stable intracellular pH. Higher unsaturated and cyclopropane fatty acid levels resulted in increased membrane fluidity and compactness and decreased ATP levels to support the energy requirements for stress resistance. Initially, H+-ATPase activity increased to provide energy for proton output and decreased later at higher copper ion stress. From transcriptome analysis, 140 genes were differentially expressed under low copper stress (1 g/L), while 250 genes exhibited altered transcriptional levels at higher copper stress (3 g/L). These differentially expressed genes were involved primarily in metabolic pathways such as energy metabolism, two-component systems, amino acid metabolism, and signal transduction. The Sox family cluster gene cluster involved in the conversion of thiosulfate to sulfate was upregulated in the sulfur metabolism pathway. In the oxidative phosphorylation pathway, genes participating in the synthesis of NADH oxidoreductase and cytochrome c oxidase, nuoL, cyoABD (cyoA, cyoB and cyoD) and cydAB (cydA and cydB), were downregulated. The TCS element ompR, closely associated with the osmotic pressure, exhibited active response, while Cu2+ efflux system gene cusRS was upregulated. In the amino acid metabolism, the glnA involved in nitrogen fixation was upregulated and promoted the synthesis of glutamine synthetase for reducing excessive oxidative stress. This study provides new insights into the mechanism underlying A. caldus response to heavy-metal ion stress under harsh bioleaching conditions.

中文翻译：

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代谢转录分析中度嗜热生物浸提微生物嗜酸硫杆菌的铜耐受性。

生物浸出是一种替代性的环境冶炼技术，通常会使用高浓度的重金属离子，特别是在后续阶段，这是由于矿物中的金属离子积累所致。在这项研究中，我们通过生理学和转录组学分析，分析了生物浸出微生物嗜酸杆菌对铜胁迫的总体反应。扫描电子显微镜结果显示铜胁迫下较高的细胞外聚合物分泌和细胞聚集。细胞内谷氨酸，甘氨酸和半胱氨酸水平增加，有利于合成谷胱甘肽以维持氧化还原状态。GSH在铜胁迫条件下，GSH-PX和CAT的活性增加，导致氧化损伤减少，同时保持稳定的细胞内pH。较高的不饱和脂肪酸和环丙烷脂肪酸含量会增加膜的流动性和致密性，并降低ATP含量，以支持抗应力的能量需求。最初，H + -ATPase活性增加为质子输出提供能量，后来在较高的铜离子应力下降低。通过转录组分析，在低铜胁迫（1 g / L）下140个基因被差异表达，而在较高铜胁迫（3 g / L）下250个基因表现出改变的转录水平。这些差异表达的基因主要参与代谢途径，例如能量代谢，两组分系统，氨基酸代谢和信号转导。在硫代谢途径中，涉及硫代硫酸盐向硫酸盐转化的Sox家族簇基因簇被上调。在氧化磷酸化途径中，参与NADH氧化还原酶和细胞色素C氧化酶，nuoL，cyoABD（cyoA，cyoB和cyoD）和cydAB（cydA和cydB）合成的基因被下调。与渗透压密切相关的TCS元素ompR表现出积极的反应，而Cu2 +外排系统基因cusRS上调。在氨基酸代谢中，参与固氮的glnA被上调，并促进了谷氨酰胺合成酶的合成，以减少过度的氧化应激。这项研究提供了新的见解，在恶劣的生物浸出条件下，卡尔德酵母对重金属离子应力的响应机理。与渗透压紧密相关的TCS元素ompR表现出积极的反应，而Cu2 +外排系统基因cusRS上调。在氨基酸代谢中，参与固氮的glnA被上调，并促进了谷氨酰胺合成酶的合成，以减少过度的氧化应激。这项研究提供了新的见解，在恶劣的生物浸出条件下，卡尔德酵母对重金属离子应力的响应机理。与渗透压密切相关的TCS元素ompR表现出积极的反应，而Cu2 +外排系统基因cusRS上调。在氨基酸代谢中，参与固氮的glnA被上调，并促进了谷氨酰胺合成酶的合成，以减少过度的氧化应激。这项研究提供了新的见解，在恶劣的生物浸出条件下，卡尔德酵母对重金属离子应力的响应机理。