Properties of ferric-ion reducing system of T. ferrooxidans and molecular cloning of this enzyme

氧化铁硫杆菌生活在酸性矿山的排水系统中，对硫化矿的细菌浸出起着至关重要的作用。氧化亚铁杆菌在细菌浸出中的价值可能是由于这种细菌氧化亚铁离子和还原硫化合物的能力。为了获得更多有价值的细菌浸出菌株，研究氧化亚铁杆菌中硫氧化的机理十分重要。在本项目中获得了以下结果：(1)澄清了T. ferrooxidans AP19-3中存在一种新的硫氧化酶或硫铁离子氧化还原酶（SFORase），并将其纯化为电泳均相状态。(2)在T. ferrooxidans中提出了一种新的硫氧化途径，即单质硫通过SFORase、亚硫酸盐、铁离子氧化还原酶和铁氧化酶三种酶的协同氧化，Fe^<3+>和Fe^<2+>在这些酶之间起电子介质的作用。(3)提出了这种新的硫氧化途径实际上涉及该细菌的好氧硫氧化的证据。(4)明确了Cu^<2+>和Co^<2+>抑制T. ferrooxidans硫代谢的机理。(5)明确了T. ferrooxidans用单质硫还原Mn^<4+>和Mo^<6+>的机理。(6)测定了SFORase n端氨基酸序列。

The iron-oxidizing bacterium Thiobacillus ferrooxidans inhabits drainage in acid mines and plays a crucial role in the bacterial leaching of sulfide ores. The value of T. ferrooxidans in bacterial leaching may be due to the ability of this bacterium to oxidize both ferrous ions and reduced sulfur compounds. In order to obtain more valuable strains for bacterial leaching, it is important to study the mechanism of sulfur-oxidation in T. ferrooxidans. The folloing results were obtained in this project. (1) The existence of a novel sulfur-oxidizing enzymes or sulfur:ferric ion oxidoreductase (SFORase) was clarified in T. ferrooxidans AP19-3 and it was purified to an electrophoretically homogenous state. (2) A new route for sulfur oxidation other than that previously reported was proposed in T. ferrooxidans, in which elemental sulfur is oxidized by the cooperation of three enzymes, namely, the SFORase, sulfite:ferric ion oxidoreductase and iron oxidase, and Fe^<3+> and Fe^<2+> play a role as mediator of electrons among these enzymes. (3) Evidence that this new sulfur oxidation route actually involves in aerobic sulfur oxidation by this bacterium was pressented. (4) The mechanism for the inhibition by Cu^<2+> and Co^<2+> of the sulfur metabolism of T. ferrooxidans was clarified. (5) The mechanisms for Mn^<4+> and Mo^<6+> reduction with elemental sulfur by T. ferrooxidans were clarified. (6) N-terminal amino acid sequence of SFORase was determined.