Navarro Claudio A, Orellana Luis H, Mauriaca Cecilia, Jerez Carlos A
Department of Biology, Laboratory of Molecular Microbiology and Biotechnology, Faculty of Sciences, Millennium Institute for Cell Dynamics andBiotechnology, University of Chile, Santiago, Chile.
Appl Environ Microbiol. 2009 Oct;75(19):6102-9. doi: 10.1128/AEM.00308-09. Epub 2009 Aug 7.
The acidophilic Acidithiobacillus ferrooxidans can resist exceptionally high copper (Cu) concentrations. This property is important for its use in biomining processes, where Cu and other metal levels range usually between 15 and 100 mM. To learn about the mechanisms that allow A. ferrooxidans cells to survive in this environment, a bioinformatic search of its genome showed the presence of at least 10 genes that are possibly related to Cu homeostasis. Among them are three genes coding for putative ATPases related to the transport of Cu (A. ferrooxidans copA1 [copA1(Af)], copA2(Af), and copB(Af)), three genes related to a system of the resistance nodulation cell division family involved in the extraction of Cu from the cell (cusA(Af), cusB(Af), and cusC(Af)), and two genes coding for periplasmic chaperones for this metal (cusF(Af) and copC(Af)). The expression of most of these open reading frames was studied by real-time reverse transcriptase PCR using A. ferrooxidans cells adapted for growth in the presence of high concentrations of Cu. The putative A. ferrooxidans Cu resistance determinants were found to be upregulated when this bacterium was exposed to Cu in the range of 5 to 25 mM. These A. ferrooxidans genes conferred to Escherichia coli a greater Cu resistance than wild-type cells, supporting their functionality. The results reported here and previously published data strongly suggest that the high resistance of the extremophilic A. ferrooxidans to Cu may be due to part or all of the following key elements: (i) a wide repertoire of Cu resistance determinants, (ii) the duplication of some of these Cu resistance determinants, (iii) the existence of novel Cu chaperones, and (iv) a polyP-based Cu resistance system.
嗜酸氧化亚铁硫杆菌能够耐受极高浓度的铜（Cu）。这一特性对于其在生物采矿过程中的应用至关重要，在生物采矿过程中，铜和其他金属的浓度通常在15至100 mM之间。为了解氧化亚铁硫杆菌细胞在这种环境中存活的机制，对其基因组进行的生物信息学搜索显示，至少有10个基因可能与铜稳态有关。其中包括三个编码与铜转运相关的假定ATP酶的基因（氧化亚铁硫杆菌copA1 [copA1(Af)]、copA2(Af)和copB(Af)），三个与参与从细胞中提取铜的抗药结节性细胞分裂家族系统相关的基因（cusA(Af)、cusB(Af)和cusC(Af)），以及两个编码这种金属的周质伴侣蛋白的基因（cusF(Af)和copC(Af)）。使用适应在高浓度铜存在下生长的氧化亚铁硫杆菌细胞，通过实时逆转录PCR研究了这些开放阅读框中大多数的表达。当这种细菌暴露于5至25 mM范围内的铜时，发现假定的氧化亚铁硫杆菌铜抗性决定因素会上调。这些氧化亚铁硫杆菌基因赋予大肠杆菌比野生型细胞更强的铜抗性，支持了它们的功能。本文报道的结果和先前发表的数据有力地表明，极端嗜酸的氧化亚铁硫杆菌对铜的高抗性可能部分或全部归因于以下关键因素：（i）广泛的铜抗性决定因素库，（ii）其中一些铜抗性决定因素的重复，（iii）新型铜伴侣蛋白的存在，以及（iv）基于多聚磷酸盐的铜抗性系统。
