Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, SK-043 53 Kosice, Slovakia.
Res Microbiol. 2009 Dec;160(10):767-74. doi: 10.1016/j.resmic.2009.08.022. Epub 2009 Sep 24.
Mesophilic iron and sulfur-oxidizing acidophiles are readily found in acid mine drainage sites and bioleaching operations, but relatively little is known about their activities at suboptimal temperatures and in cold environments. The purpose of this work was to characterize the oxidation of elemental sulfur (S(0)), tetrathionate (S4O6(2-)) and ferrous iron (Fe2+) by the psychrotolerant Acidithiobacillus strain SS3. The rates of elemental sulfur and tetrathionate oxidation had temperature optima of 20 degrees and 25 degrees C, respectively, determined using a temperature gradient incubator that involved narrow (1.1 degrees C) incremental increases from 5 degrees to 30 degrees C. Activation energies calculated from the Arrhenius plots were 61 and 89 kJ mol(-1) for tetrathionate and 110 kJ mol(-1) for S(0) oxidation. The oxidation of elemental sulfur produced sulfuric acid at 5 degrees C and decreased the pH to approximately 1. The low pH inhibited further oxidation of the substrate. In media with both S(0) and Fe2+, oxidation of elemental sulfur did not commence until all available ferrous iron was oxidized. These data on sequential oxidation of the two substrates are in keeping with upregulation and downregulation of several proteins previously noted in the literature. Ferric iron was reduced to Fe2+ in parallel with elemental sulfur oxidation, indicating the presence of a sulfur:ferric iron reductase system in this bacterium.
嗜中温、嗜酸硫铁氧化菌在酸性矿山排水和生物浸出作业中很容易被发现，但人们对它们在非最适温度和寒冷环境中的活性却知之甚少。本研究的目的是研究耐冷的嗜酸硫杆菌（Acidithiobacillus strain SS3）对单质硫（S(0)）、连四硫酸盐（S4O6(2-)）和二价铁（Fe2+）的氧化作用。采用温度梯度孵育器，以 5°C 至 30°C 的窄幅（1.1°C）递增方式，从 5°C 开始逐渐升温，分别确定了单质硫和连四硫酸盐氧化的温度最佳值为 20°C 和 25°C。从阿累尼乌斯图计算出的活化能分别为 61kJ/mol 和 89kJ/mol，用于连四硫酸盐和单质硫氧化，而单质硫氧化的活化能为 110kJ/mol。在 5°C 下，单质硫的氧化会产生硫酸，并将 pH 值降低到约 1。低 pH 值会抑制底物的进一步氧化。在同时含有 S(0)和 Fe2+的培养基中，只有所有可用的二价铁被氧化后，单质硫的氧化才会开始。这些关于两种底物顺序氧化的实验数据与文献中先前报道的几种蛋白质的上调和下调相一致。单质硫氧化的同时，三价铁被还原为二价铁，这表明该细菌中存在一种硫：三价铁还原酶系统。
