Microbial degradation kinetics and molecular mechanism of 2,6-dichloro-4-nitrophenol by a Cupriavidus strain
Microbial degradation kinetics and molecular mechanism of 2,6-dichloro-4-nitrophenol by a Cupriavidus strain
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Cupriavidus菌株对2,6-二氯-4-硝基苯酚的微生物降解动力学和分子机制
DOI：
10.1016/j.envpol.2019.113703
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发表时间：
2020-03-01
影响因子：
8.9
通讯作者：
Hu, Xiaoke
中科院分区：
文献类型：
--
作者：
Min, Jun;Xu, Lingxue;Hu, Xiaoke
2，6-二氯-4-硝基苯酚（2，6-DCNP）是一种新型的氯代硝基芳烃污染物，其在环境中的归趋是一个重要的研究课题。然而，具有利用2，6-DCNP能力的微生物尚未报道。在本研究中，先前已报道可降解各种卤代硝基酚的贪铜菌CNP-8被证实也能够降解2，6-DCNP。生物降解动力学实验表明，它降解2，6-DCNP的比生长速率为0.124 h（-1），半饱和常数为0.038 mM，抑制常数为0.42 mM。实时定量PCR分析表明，hnp基因簇参与了2，6-DCNP的分解代谢。通过Ni-NTA层析将hnpA和hnpB基因产物纯化至均一。酶促分析表明，HnpAB，一种FAD依赖性双组分单加氧酶，将2，6-DCNP转化为6-氯羟基喹啉，Km为3.9 +/- 1.4 μ M，k（cat）/K-m为0.12 +/- 0.04 μ M-1 min（-1）。作为加氧酶组分的编码基因，hnpA通过基因敲除和互补作用是CNP-8在2，6-DCNP上生长所必需的。系统发育分析表明，该簇起源于氯酚类化合物的催化簇，而不是硝基酚类化合物。据我们所知，CNP-8是第一个具有利用2，6-DCNP能力的细菌，该研究填补了该污染物在分子、生化和遗传水平上微生物降解机制的空白。此外，菌株CNP-8还能快速降解人工合成废水中的3种氯代硝基酚，表明其在氯代硝基酚污染环境的生物修复中具有潜在应用价值。(C)2019爱思唯尔有限公司版权所有。
2,6-Dichloro-4-nitrophenol (2,6-DCNP) is an emerging chlorinated nitroaromatic pollutant, and its fate in the environment is an important question. However, microorganisms with the ability to utilize 2,6-DCNP have not been reported. In this study, Cupriavidus sp. CNP-8 having been previously reported to degrade various halogenated nitrophenols, was verified to be also capable of degrading 2,6-DCNP. Biodegradation kinetics assay showed that it degraded 2,6-DCNP with the specific growth rate of 0.124 h(-1), half saturation constant of 0.038 mM and inhibition constant of 0.42 mM. Reai-time quantitative PCR analyses indicated that the hnp gene cluster was involved in the catabolism of 2,6-DCNP. The hnpA and hnpB gene products were purified to homogeneity by Ni-NTA chromatography. Enzymatic assays showed that HnpAB, a FAD-dependent two-component monooxygenase, converted 2,6-DCNP to 6-chlorohydroxyquinol with a K-m of 3.9 +/- 1.4 mu M and a k(cat)/K-m of 0.12 +/- 0.04 mu M-1 min(-1). As the oxygenase component encoding gene, hnpA is necessary for CNP-8 to grow on 2,6-DCNP by gene knockout and complementation. The phylogenetic analysis showed that the hnp cluster originated from the cluster involved in the catabolism of chlorophenols rather than nitrophenols. To our knowledge, CNP-8 is the first bacterium with the ability to utilize 2,6-DCNP, and this study fills a gap in the microbial degradation mechanism of this pollutant at the molecular, biochemical and genetic levels. Moreover, strain CNP-8 could degrade three chlorinated nitrophenols rapidly from the synthetic wastewater, indicating its potential in the bioremediation of chlorinated nitrophenols polluted environments. (C) 2019 Elsevier Ltd. All rights reserved.