Thorgersen Michael P, Lancaster W Andrew, Vaccaro Brian J, Poole Farris L, Rocha Andrea M, Mehlhorn Tonia, Pettenato Angelica, Ray Jayashree, Waters R Jordan, Melnyk Ryan A, Chakraborty Romy, Hazen Terry C, Deutschbauer Adam M, Arkin Adam P, Adams Michael W W
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA.
Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.
Appl Environ Microbiol. 2015 Aug;81(15):4976-83. doi: 10.1128/AEM.00917-15. Epub 2015 May 15.
The concentrations of molybdenum (Mo) and 25 other metals were measured in groundwater samples from 80 wells on the Oak Ridge Reservation (ORR) (Oak Ridge, TN), many of which are contaminated with nitrate, as well as uranium and various other metals. The concentrations of nitrate and uranium were in the ranges of 0.1 μM to 230 mM and <0.2 nM to 580 μM, respectively. Almost all metals examined had significantly greater median concentrations in a subset of wells that were highly contaminated with uranium (≥126 nM). They included cadmium, manganese, and cobalt, which were 1,300- to 2,700-fold higher. A notable exception, however, was Mo, which had a lower median concentration in the uranium-contaminated wells. This is significant, because Mo is essential in the dissimilatory nitrate reduction branch of the global nitrogen cycle. It is required at the catalytic site of nitrate reductase, the enzyme that reduces nitrate to nitrite. Moreover, more than 85% of the groundwater samples contained less than 10 nM Mo, whereas concentrations of 10 to 100 nM Mo were required for efficient growth by nitrate reduction for two Pseudomonas strains isolated from ORR wells and by a model denitrifier, Pseudomonas stutzeri RCH2. Higher concentrations of Mo tended to inhibit the growth of these strains due to the accumulation of toxic concentrations of nitrite, and this effect was exacerbated at high nitrate concentrations. The relevance of these results to a Mo-based nitrate removal strategy and the potential community-driving role that Mo plays in contaminated environments are discussed.
对田纳西州橡树岭保留地（ORR）80口水井的地下水样本中的钼（Mo）和其他25种金属的浓度进行了测量，其中许多水井受到硝酸盐、铀和各种其他金属的污染。硝酸盐和铀的浓度范围分别为0.1μM至230 mM以及<0.2 nM至580μM。几乎所有检测的金属在一组被铀高度污染（≥126 nM）的水井中的中位浓度都显著更高。其中包括镉、锰和钴，其浓度高出1300至2700倍。然而，一个显著的例外是钼，其在受铀污染的水井中的中位浓度较低。这很重要，因为钼在全球氮循环的异化硝酸盐还原分支中至关重要。它是硝酸盐还原酶催化位点所必需的，该酶将硝酸盐还原为亚硝酸盐。此外，超过85%的地下水样本中钼含量低于10 nM，而从ORR水井分离出的两种假单胞菌菌株以及模式反硝化菌斯氏假单胞菌RCH2通过硝酸盐还原实现高效生长需要10至100 nM的钼浓度。较高浓度的钼由于亚硝酸盐的毒性浓度积累往往会抑制这些菌株的生长，并且在高硝酸盐浓度下这种效应会加剧。讨论了这些结果与基于钼的硝酸盐去除策略的相关性以及钼在受污染环境中可能发挥的群落驱动作用。
