Microbial cycling of iron in acidic fens

操纵实验表明，增加沼泽Schlöppnerbrunnen泥炭通气并没有消除酶锁存假说所预测的限制CO2再释放到大气中的关键机制。然而，操作更新了备选电子受体池，并将电子流从CH4形成转移到备选过程。土壤微观环境中形成了乙酸，但对CH4形成或Fe（III）还原的刺激较小。令人惊讶的是，重新润湿后，铁（II）的形成速度没有提高，但时间延长了，所有土壤深度的铁（II）形成的最大量都增加了，这表明铁（II）从较深的土壤层中被动员并随后氧化。因此，本项目的假设是，由于铁（II）氧化细菌沉积的铁矿物，增加的干燥和再湿润事件有利于微生物铁（III）的还原，特别是在地表以下的泥炭层中。项目2的主要目标是：(1)确定干燥和再湿事件是否影响活性铁（III）还原菌群的丰度，(2)估计铁（II）氧化菌在多大程度上参与了铁矿物的沉积，(3)阐明参与醋酸盐氧化的微生物群。

The manipulation experiments indicated that increased peat aeration at the fen Schlöppnerbrunnen did not eliminate the critical mechanism restricting the re-release of CO2 to the atmosphere as predicted by the enzymic latch hypothesis. However, manipulation renewaled the pool of alternative electron acceptors and shifted the electron flow from CH4 formation to alternative processes. Acetate was formed in soil microcosms, but the stimulation of CH4 formation or Fe(III) reduction was small. Surprisingly not the rate of Fe(II) formation was enhanced after rewetting but the time period was elongated, and maximum amount of Fe(II) formed increased in all soil depths suggesting a mobilization and subsequent oxidation of Fe(II) from deeper reduced soil horizons. Thus, the hypothesis of this project is that increased drying and rewetting events favor microbial Fe(III) reduction especially in peat layers below the surface due to iron minerals deposited by Fe(II) oxidizing bacteria. The main goals of project 2 are (1) to determine if drying and rewetting events affect the abundance of the active Fe(III)-reducing populations, (2) to estimate to which extent Fe(II)-oxidizing bacteria are involved in the deposition of iron minerals, and (3) to elucidate the microbial population involved in the oxidation of acetate.