Collaborative Research: Oxygen Isotope Tracers of Bacterial Manganese Oxidation

导致地质金属矿床形成的反应是复杂的，微生物在一些低温矿床形成中的潜在作用虽然得到了承认，但尚未得到充分评估。在过去的9个月里，研究人员开发了测量锰氧化物的18O的技术，并利用这些测量来比较微生物和非生物的锰氧化机制。他们推测，锰氧化物氧同位素组成的测量可以作为锰矿床微生物来源的地质示踪，或作为形成矿床的水的溶解氧含量的古指示器，从而确定形成矿床的水的条件。在确定这一方法的技术可行性方面取得了进展。他们将继续使用氧同位素来研究化学和生物氧化锰(II)的机制，并确定在环境条件下锰氧化物的同位素特征是否持续存在。首先，他们将通过与生物和化学沉淀的不同氧化锰矿物进行一系列交换实验来评估氧化锰中氧示踪剂的稳定性。其次，他们将通过测量初始和剩余反应物(O2)以及氧化锰产物的18O来确定细菌在Mn(II)氧化过程中是否产生分级氧同位素。第三，将通过培养各种锰(II)氧化菌并测量其氧化物的18O来研究微生物机制的多样性。最后，将在现场的缺氧水柱中测试溶解氧浓度和锰氧化物的18O之间的关系，从黑海的初步研究开始，最终到达一个缺氧海洋峡湾的两次巡航。该研究对古环境研究具有重要意义。

The reactions leading to the formation of geological metal ore deposits are complex, and the potential role of microorganisms in the formation of some low-temperature ore deposits, while recognized, has not been fully assessed. In the past 9 months the investigators developed techniques for measuring the 18O of manganese oxides and are using these measurements to compare microbial and nonbiological manganese oxidation mechanisms. They hypothesize that measurements of the oxygen isotopic composition of Mn oxides can be used as geologic tracers for the microbial origin of Mn deposits or as a paleoindicator of the dissolved oxygen content, and there fore Eh conditions, of the water from which the deposit was formed. Progress has been made in establishing the technical feasibility of this approach. They will continue using oxygen isotopes to examine mechanisms of chemical and biological Mn(II) oxidation and determine if the isotopic signature of Mn oxides persist under environmental conditions. First, they will assess the stability of the oxygen tracer in the manganese oxide by a series of exchange experiments with different Mn oxide minerals precipitated biologically and chemically. Second, they will determine if bacteria fractionate oxygen isotopes during Mn(II) oxidation by measuring the 18O of the initial and residual reactant (O2) as well as the Mn oxide product. Third, the diversity of microbial mechanisms will be investigated by culturing a variety of Mn(ii) oxidizing bacteria and measuring the 18O of their oxides. Last, the relationship between dissolved oxygen concentration and the 18O of the manganese oxides will be tested in the field in anoxic water columns beginning with initial studies in the Black Sea and culminating in two cruises to an anoxic marine fjord. This research has significant implications for paleoenvironmental studies.