Thiosulfate oxidation by Thiomicrospira thermophila: metabolic flexibility in response to ambient geochemistry.
Thiosulfate oxidation by Thiomicrospira thermophila: metabolic flexibility in response to ambient geochemistry.
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DOI：
10.1111/1462-2920.13232
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发表时间：
2016-09
影响因子：
5.1
通讯作者：
Fike DA
中科院分区：
文献类型：
--
作者：
Houghton JL;Foustoukos DI;Flynn TM;Vetriani C;Bradley AS;Fike DA
先前对无色硫细菌氧化硫代硫酸盐的化学计量的研究未能证明硫的质量平衡，这表明一定存在未识别的氧化产物。在这里，我们介绍了从东太平洋海隆的扩散热液中分离出来的嗜热硫微螺菌株 EPR85 在不同 pH 条件下生长过程中的反应化学计量和动力学。在 pH 8.0 时，硫代硫酸盐按化学计量转化为硫酸盐。在较低pH值下，硫代硫酸盐氧化的产物是细胞外元素硫和硫酸盐。我们能够重复之前的实验，并将缺失的硫鉴定为连四硫酸盐，这与之前关于硫代硫酸盐脱氢酶活性的报道一致。在微酸性条件下形成连四硫酸盐。来自嗜热丝虫菌株 EPR85 的基因组 DNA 含有与 Sox 途径 (soxAXYZBCDL) 中的基因同源的基因，以及硫氰酸酶和硫代硫酸盐脱氢酶。没有其他含有 sox(CD)2 基因的硫氧化细菌产生细胞外元素硫的报道。如果我们在嗜热热丝菌中观察到的明显修饰的 Sox 途径也存在于海洋硫杆菌和硫微螺菌属物种中，那么细胞外元素硫的产生可能在海洋硫循环中具有重要的生物地球化学意义。
Previous studies of the stoichiometry of thiosulfate oxidation by colorless sulfur bacteria have failed to demonstrate mass balance of sulfur, indicating that unidentified oxidized products must be present. Here we present reaction stoichiometry and kinetics under variable pH conditions during the growth of Thiomicrospira thermophila strain EPR85, isolated from diffuse hydrothermal fluids at the East Pacific Rise. At pH 8.0, thiosulfate is stoichiometrically converted to sulfate. At lower pH, the products of thiosulfate oxidation are extracellular elemental sulfur and sulfate. We were able to replicate previous experiments and identify the missing sulfur as tetrathionate, consistent with previous reports of the activity of thiosulfate dehydrogenase. Tetrathionate was formed under slightly acidic conditions. Genomic DNA from T. thermophila strain EPR85 contains genes homologous to those in the Sox pathway (soxAXYZBCDL), as well as rhodanese and thiosulfate dehydrogenase. No other sulfur oxidizing bacteria containing sox(CD)2 genes have been reported to produce extracellular elemental sulfur. If the apparent modified Sox pathway we observe in T. thermophila is present in marine Thiobacillus and Thiomicrospira species, production of extracellular elemental sulfur may be biogeochemically important in marine sulfur cycling.