Biodegradation of 3-Chloronitrobenzene and 3-Bromonitrobenzene by Diaphorobacter sp. Strain JS3051
Biodegradation of 3-Chloronitrobenzene and 3-Bromonitrobenzene by Diaphorobacter sp. Strain JS3051
复制标题
DOI：
10.1128/aem.02437-21
复制
发表时间：
2022-03
影响因子：
4.4
通讯作者：
Zhihui Xu;J. Spain;N. Zhou;Tao Li
中科院分区：
文献类型：
--
作者：
Zhihui Xu;J. Spain;N. Zhou;Tao Li
卤代硝基芳香族化合物是一种持久性的环境污染物，其中一些已被证明可被细菌降解。降解3-氯硝基苯和3-溴代苯的天然菌株尚未见报道。摘要卤代硝基苯是一种有毒的化学中间体，广泛用于染料和农药的工业合成。能够降解2-和4-氯硝基苯的细菌已经被分离和鉴定；相比之下，还没有自然菌株降解间卤代硝基苯的报道。在本研究中，黄杆菌属(Diaphorbacter sp.)据报道，菌株JS3051能降解2，3-二氯硝基苯，能在3-氯硝基苯和3-溴代苯上生长，但不能在3-氟硝基苯上生长，这是碳、氮和能源的唯一来源。Rieske非血红素铁双加氧酶(DcbAaAbAcAd)催化3-氯硝基苯和3-溴代苯的二羟化反应，产生区域特异性的开环中间体4-氯邻苯二酚和4-溴邻苯二酚。DcbAaAbAcAd对3-氟硝基苯的低活性和松弛的区域专一性可能是由于氟原子的电负性较高，阻碍了它与活性中心的E204残基相互作用。DCCA是一种氯代邻苯二酚1，2-双加氧酶，它能将4-氯代邻苯二酚和4-溴邻苯二酚转化为相应的卤代琥珀酸，催化效率高，但对氟代邻苯二酚类似物的Kcat/Km值要低得多。结果表明，黄杆菌的DCB和DCC酶活性较高。菌株JS3051除能催化降解2，3-二氯硝基苯外，还能催化降解3-氯代苯和3-溴代苯。在被氯硝基苯混合物污染的栖息地，利用多种底物的能力将提供很强的选择性优势。重要性卤代硝基芳香族化合物是一种持久性的环境污染物，其中一些已被证明可被细菌降解。降解3-氯硝基苯和3-溴代苯的天然菌株尚未见报道。在本研究中，我们报道了黄杆菌属。菌株JS3051对2，3-二氯硝基苯、3-氯硝基苯和3-溴代苯具有相同的降解途径，但不能在3-氟硝基苯上生长。根据生化分析，可以得出结论，最初的双加氧酶和低途径酶对3-氟硝基苯的效率低下，甚至错位中间体，这可能是导致3-氟硝基苯无法生长的原因。这些结果促进了我们对分解代谢酶的广泛底物特异性如何使细菌适应外来污染物混合物的栖息地的理解。
Halonitroaromatic compounds are persistent environmental contaminants, and some of them have been demonstrated to be degraded by bacteria. Natural isolates that degrade 3-chloronitrobenzene and 3-bromonitrobenzene have not been reported. ABSTRACT Halonitrobenzenes are toxic chemical intermediates used widely for industrial synthesis of dyes and pesticides. Bacteria able to degrade 2- and 4-chloronitrobenzene have been isolated and characterized; in contrast, no natural isolate has been reported to degrade meta-halonitrobenzenes. In this study, Diaphorobacter sp. strain JS3051, previously reported to degrade 2,3-dichloronitrobenzene, grew readily on 3-chloronitrobenzene and 3-bromonitrobenzene, but not on 3-fluoronitrobenzene, as sole sources of carbon, nitrogen, and energy. A Rieske nonheme iron dioxygenase (DcbAaAbAcAd) catalyzed the dihydroxylation of 3-chloronitrobenzene and 3-bromonitrobenzene, resulting in the regiospecific production of ring-cleavage intermediates 4-chlorocatechol and 4-bromocatechol. The lower activity and relaxed regiospecificity of DcbAaAbAcAd toward 3-fluoronitrobenzene is likely due to the higher electronegativity of the fluorine atom, which hinders it from interacting with E204 residue at the active site. DccA, a chlorocatechol 1,2-dioxygenase, converts 4-chlorocatechol and 4-bromocatechol into the corresponding halomuconic acids with high catalytic efficiency, but with much lower Kcat/Km values for fluorocatechol analogues. The results indicate that the Dcb and Dcc enzymes of Diaphorobacter sp. strain JS3051 can catalyze the degradation of 3-chloro- and 3-bromonitrobenzene in addition to 2,3-dichloronitrobenzene. The ability to utilize multiple substrates would provide a strong selective advantage in a habitat contaminated with mixtures of chloronitrobenzenes. IMPORTANCE Halonitroaromatic compounds are persistent environmental contaminants, and some of them have been demonstrated to be degraded by bacteria. Natural isolates that degrade 3-chloronitrobenzene and 3-bromonitrobenzene have not been reported. In this study, we report that Diaphorobacter sp. strain JS3051 can degrade 2,3-dichloronitrobenzene, 3-chloronitrobenzene, and 3-bromonitrobenzene using the same catabolic pathway, whereas it is unable to grow on 3-fluoronitrobenzene. Based on biochemical analyses, it can be concluded that the initial dioxygenase and lower pathway enzymes are inefficient for 3-fluoronitrobenzene and even misroute the intermediates, which is likely responsible for the failure to grow. These results advance our understanding of how the broad substrate specificities of catabolic enzymes allow bacteria to adapt to habitats with mixtures of xenobiotic contaminants.