Thiosulphate oxidation in the phototrophic sulphur bacterium Allochromatium vinosum
Thiosulphate oxidation in the phototrophic sulphur bacterium Allochromatium vinosum
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DOI：
10.1111/j.1365-2958.2006.05408.x
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发表时间：
2006-11-01
影响因子：
3.6
通讯作者：
Dahl, Christiane
中科院分区：
文献类型：
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作者：
Hensen, Daniela;Sperling, Detlef;Dahl, Christiane
在紫硫杆菌中，硫代硫酸盐的氧化存在两种不同的途径：氧化为四硫酸盐和完全氧化为硫酸盐，中间产物为硫球。四硫酸盐：硫酸盐的比例强烈地依赖于pH，在酸性条件下形成四硫酸盐是首选的。硫代硫酸盐脱氢酶是一种结构性表达的30 kDa c型细胞色素单体，其最适pH为4.2，催化四硫酸盐的形成。一种周质硫酸盐氧化多酶复合体(SOX)被描述为在化学营养和光养硫氧化物中由硫代硫酸盐生成硫酸盐的原因，这些化学和光养硫氧化物不形成硫磺沉积物。在固硫黄曲霉中，我们在两个独立的基因座(soxBXA和soxYZ)上发现了5个SOX基因。对于SoxA，观察到了硫代硫酸盐依赖的表达诱导，高于低组成水平。纯化了3个SOX编码蛋白：异二聚体C型细胞色素SoxXA、单体SoxB和异二聚体SoxYZ。基因失活和互补实验证明，这些蛋白质是硫代硫酸盐氧化成硫酸盐所必需的。黄曲霉中硫球的中间形成似乎与soxCD基因的缺失有关，该基因的产物被认为是氧化SOX结合的硫烷硫的产物。在没有它们的情况下，后者被转移到不断生长的硫球中。
Two different pathways for thiosulphate oxidation are present in the purple sulphur bacterium Allochromatium vinosum: oxidation to tetrathionate and complete oxidation to sulphate with obligatory formation of sulphur globules as intermediates. The tetrathionate:sulphate ratio is strongly pH-dependent with tetrathionate formation being preferred under acidic conditions. Thiosulphate dehydrogenase, a constitutively expressed monomeric 30 kDa c-type cytochrome with a pH optimum at pH 4.2 catalyses tetrathionate formation. A periplasmic thiosulphate-oxidizing multienzyme complex (Sox) has been described to be responsible for formation of sulphate from thiosulphate in chemotrophic and phototrophic sulphur oxidizers that do not form sulphur deposits. In the sulphur-storing A. vinosum we identified five sox genes in two independent loci (soxBXA and soxYZ). For SoxA a thiosulphate-dependent induction of expression, above a low constitutive level, was observed. Three sox-encoded proteins were purified: the heterodimeric c-type cytochrome SoxXA, the monomeric SoxB and the heterodimeric SoxYZ. Gene inactivation and complementation experiments proved these proteins to be indispensable for thiosulphate oxidation to sulphate. The intermediary formation of sulphur globules in A. vinosum appears to be related to the lack of soxCD genes, the products of which are proposed to oxidize SoxY-bound sulphane sulphur. In their absence the latter is instead transferred to growing sulphur globules.