Exogenous nitrate attenuates nitrite toxicity to anaerobic ammonium oxidizing (anammox) bacteria.
Exogenous nitrate attenuates nitrite toxicity to anaerobic ammonium oxidizing (anammox) bacteria.
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DOI：
10.1016/j.chemosphere.2015.11.013
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发表时间：
2016-02
期刊：
影响因子：
8.8
通讯作者：
Guangbin Li;David Vilcherrez;J. Carvajal-Arroyo;R. Sierra-Alvarez;J. Field
中科院分区：
文献类型：
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作者：
Guangbin Li;David Vilcherrez;J. Carvajal-Arroyo;R. Sierra-Alvarez;J. Field
厌氧氨氧化细菌（anammox）可以被其主要底物之一亚硝酸盐（NO 2−）严重抑制。目前，关于厌氧氨氧化细菌能够耐受有毒NO 2−的过程的信息有限。细胞内消耗或电化学驱动（跨膜质子动力）的NO2 −输出被认为是NO2 −解毒的主要机制。在这项工作中，我们评估了外源性硝酸盐（NO3 −）缓解NO2 −毒性的潜力，这是由NarK（anammox基因组中编码的NO3 −/NO2 −转运蛋白）促进的。NO3 −对NO2 −解毒的相对贡献被发现是pH依赖性的。厌氧氨氧化细胞暴露于NO 2−而缺乏其供电子底物铵（NH 4+），会导致NO 2−应激。在pH 6.7和7.0时，NO2 −胁迫细胞的活性分别为非胁迫对照活性的0和27%（NO2 −和NH 4+同时进料）。在pH 6.7和7.0时，外源NO3 −的加入分别使活性恢复到对照的42%和80%。随着NO3 −浓度的增加，NO2 −应激细胞的活性恢复得到改善，在0.85 mM时达到最大恢复。由于在较低pH值下NO2 −毒性更严重，NO3 −预孵育时间在pH 7.0下比在pH 6.7下不太重要。此外，在pH 7.5的质子梯度干扰剂羰基氰间氯苯腙中，NO3-几乎完全减弱了NO2-的毒性，提供证据表明NO3-衰减与质子动力无关。在分批试验中没有可测量的NO3 −消耗（或NO3 −依赖的N2产生），使得NO2 −依赖于NO3 −的主动转运成为NO2 −抑制缓解的唯一合理解释。我们认为，厌氧氨氧化细胞可以使用二级运输系统促进外源性NO3-，以减轻NO2-毒性。
Anaerobic ammonium oxidizing bacteria (anammox) can be severely inhibited by one of its main substrates, nitrite (NO 2−). At present, there is limited information on the processes by which anammox bacteria are able to tolerate toxic NO 2−. Intracellular consumption or electrochemically driven (transmembrane proton motive force) NO 2− export are considered the main mechanisms of NO 2− detoxification. In this work, we evaluated the potential of exogenous nitrate (NO 3−) on relieving NO 2− toxicity, putatively facilitated by NarK, a NO 3−/NO 2− transporter encoded in the anammox genome. The relative contribution of NO 3− to NO 2− detoxification was found to be pH dependent. Exposure of anammox cells to NO 2− in absence of their electron donating substrate, ammonium (NH 4+), causes NO 2− stress. At pH 6.7 and 7.0, the activity of NO 2− stressed cells was respectively 0 and 27% of the non-stressed control activity (NO 2− and NH 4+ fed simultaneously). Exogenous NO 3− addition caused the recovery to 42% and 80% of the control activity at pH 6.7 and 7.0, respectively. The recovery of the activity of NO 2− stressed cells improved with increasing NO 3− concentration, the maximum recovery being achieved at 0.85 mM. The NO 3− pre-incubation time is less significant at pH 7.0 than at pH 6.7 due to a more severe NO 2− toxicity at lower pH. Additionally, NO 3− caused almost complete attenuation of NO 2− toxicity in cells exposed to the proton gradient disruptor carbonyl cyanide m-chlorophenyl hydrazone at pH 7.5, providing evidence that the NO 3− attenuation is independent of the proton motive force. The absence of a measurable NO 3− consumption (or NO 3− dependent N 2 production) during the batch tests leaves NO 3− dependent active transport of NO 2− as the only plausible explanation for the relief of NO 2− inhibition. We suggest that anammox cells can use a secondary transport system facilitated by exogenous NO 3− to alleviate NO 2− toxicity.