Laboratory for Nitrogen Fixation Research and Departments of Microbiology and Crop and Soil Sciences, Oregon State University, Corvallis, Oregon 97331-2902.
Appl Environ Microbiol. 1998 Apr;64(4):1372-8. doi: 10.1128/AEM.64.4.1372-1378.1998.
Ammonia monooxygenase (AMO) from Nitrosomonas europaea catalyzes the oxidation of ammonia to hydroxylamine and has been shown to oxidize a variety of halogenated and nonhalogenated hydrocarbons. As part of a program focused upon extending these observations to natural systems, a study was conducted to examine the influence of soil upon the cooxidative abilities of N. europaea. Small quantities of Willamette silt loam (organic carbon content, 1.8%; cation-exchange capacity, 15 cmol/kg of soil) were suspended with N. europaea cells in a soil-slurry-type reaction mixture. The oxidations of ammonia and three different hydrocarbons (ethylene, chloroethane, and 1,1,1-trichloroethane) were compared to results for controls in which no soil was added. The soil significantly inhibited nitrite production from 10 mM ammonium by N. europaea. Inhibition resulted from a combination of ammonium adsorption onto soil colloids and the exchangeable acidity of the soil lowering the pH of the reaction mixture. These phenomena resulted in a substantial drop in the concentration of NH(4) in solution (10 to 4.5 mM) and, depending upon the pH, in a reduction in the amount of available NH(3) to concentrations (8 to 80 muM) similar to the K(s) value of AMO for NH(3) ( approximately 29 muM). At a fixed initial pH (7.8), the presence of soil also modified the rates of oxidation of ethylene and chloroethane and changed the concentrations at which their maximal rates of oxidation occurred. The modifying effects of soil on nitrite production and on the cooxidation of ethylene and chloroethane could be circumvented by raising the ammonium concentration in the reaction mixture from 10 to 50 mM. Soil had virtually no effect on the oxidation of 1,1,1-trichloroethane.
来自硝酸单胞菌（Nitrosomonas europaea）的氨单加氧酶（AMO）催化氨氧化为羟胺，并已被证明可氧化多种卤代和非卤代烃。作为一项旨在将这些观察结果扩展到自然系统的计划的一部分，进行了一项研究以检查土壤对欧洲硝酸单胞菌共氧化能力的影响。将少量威拉米特粉壤土（有机碳含量为 1.8％；阳离子交换量为 15 cmol/kg 土壤）与欧洲硝酸单胞菌细胞一起悬浮在土壤泥浆型反应混合物中。将氨和三种不同烃（乙烯、氯乙烷和 1,1,1-三氯乙烷）的氧化与未添加土壤的对照结果进行了比较。土壤显著抑制了欧洲硝酸单胞菌从 10mM 铵中产生亚硝酸盐。这种抑制是由于铵吸附在土壤胶体上以及土壤的可交换酸度降低了反应混合物的 pH 值共同作用的结果。这些现象导致溶液中 NH4+的浓度大幅下降（从 10 降至 4.5mM），并且取决于 pH 值，可用 NH3 的浓度降低到类似于 AMO 对 NH3 的 Ks 值（约 29μM）的浓度（8 至 80μM）。在固定初始 pH 值（7.8）下，土壤的存在还改变了乙烯和氯乙烷的氧化速率，并改变了其最大氧化速率发生的浓度。通过将反应混合物中的铵浓度从 10mM 提高到 50mM，可以避免土壤对亚硝酸盐生成和乙烯及氯乙烷共氧化的修饰作用。土壤对 1,1,1-三氯乙烷的氧化几乎没有影响。
