Nitrate reduction functional genes and nitrate reduction potentials persist in deeper estuarine sediments. Why?
Nitrate reduction functional genes and nitrate reduction potentials persist in deeper estuarine sediments. Why?
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DOI：
10.1371/journal.pone.0094111
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Nedwell DB
中科院分区：
文献类型：
--
作者：
Papaspyrou S;Smith CJ;Dong LF;Whitby C;Dumbrell AJ;Nedwell DB
反硝化和异化硝酸还原成铵（DNRA）是在缺氧或厌氧条件下同时发生的过程，两者都竞争硝酸盐和有机碳。尽管它们具有重要的生态意义，但关于反硝化和DNRA电位及其相关功能基因如何随沉积物深度垂直变化的研究很少。沿科尔尼河口沉积物深度剖面测量的硝酸盐还原电位处于其他沉积物中硝酸盐还原率的上界，且随深度的增加和沿河口均存在强烈的减少趋势。反硝化势沿河口方向减小，向河口方向随深度的增大减小得更快。相反，DNRA势沿河口增加。16S rRNA拷贝数和硝酸盐还原基因拷贝数沿河口方向和表层向深层呈显著下降趋势。代谢潜能和功能基因在缺乏孔隙水硝酸盐的沉积物深度持续存在。基于大型动物群分布，生物扰动对硝酸盐的运移只能解释沉积物上部10 cm深度。与孔隙水硝酸盐相比，冻融氯化钾-可萃取硝酸盐池的含量高出数倍。我们假设这可能归因于细胞内硝酸盐池的硝酸盐积累的微生物，如硫菌或Beggiatoa。然而，焦磷酸测序分析没有检测到任何这样的生物，留下其他细菌，微底栖藻类，或有孔虫，它们也被证明可以积累硝酸盐，作为可能的候选人。可氯化钾提取的硝酸盐沉积物池的重要性和生物利用度仍有待检验。不同硝酸盐还原基因系统型在垂直格局和丰度上的显著差异合理地说明了它们在整个沉积物柱中的活性差异。这就提出了一个有趣的问题，即各种硝酸盐还原酶的替代代谢作用可能是什么，类似于亚硝酸盐还原酶的替代代谢作用。
Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the sediment column. This raises interesting questions as to what the alternative metabolic roles for the various nitrate reductases could be, analogous to the alternative metabolic roles found for nitrite reductases.
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影响因子：
4.4
作者：
Dong, LF;Nedwell, DB;Rusmana, I
通讯作者：
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影响因子：
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影响因子：
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作者：
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