Biocapteurs Analyses Environnement (BAE), University of Perpignan Via Domitia, 66860, Perpignan, France.
Laboratoire de Chimie des Biomolécules et de l'Environnement-CRIOBE-USR 3278 CNRS EPHE, University of Perpignan Via Domitia, 66860, Perpignan, France.
Environ Sci Pollut Res Int. 2016 Mar;23(5):4138-48. doi: 10.1007/s11356-015-4544-1. Epub 2015 Apr 24.
In this study, a bacterial strain able to use sulcotrione, a β-triketone herbicide, as sole source of carbon and energy was isolated from soil samples previously treated with this herbicide. Phylogenetic study based on16S rRNA gene sequence showed that the isolate has 100 % of similarity with several Bradyrhizobium and was accordingly designated as Bradyrhizobium sp. SR1. Plasmid profiling revealed the presence of a large plasmid (>50 kb) in SR1 not cured under nonselective conditions. Its transfer to Escherichia coli by electroporation failed to induce β-triketone degrading capacity, suggesting that degrading genes possibly located on this plasmid cannot be expressed in E. coli or that they are not plasmid borne. The evaluation of the SR1 ability to degrade various synthetic (mesotrione and tembotrione) and natural (leptospermone) triketones showed that this strain was also able to degrade mesotrione. Although SR1 was able to entirely dissipate both herbicides, degradation rate of sulcotrione was ten times higher than that of mesotrione, showing a greater affinity of degrading-enzyme system to sulcotrione. Degradation pathway of sulcotrione involved the formation of 2-chloro-4-mesylbenzoic acid (CMBA), previously identified in sulcotrione degradation, and of a new metabolite identified as hydroxy-sulcotrione. Mesotrione degradation pathway leads to the accumulation of 4-methylsulfonyl-2-nitrobenzoic acid (MNBA) and 2-amino-4 methylsulfonylbenzoic acid (AMBA), two well-known metabolites of this herbicide. Along with the dissipation of β-triketones, one could observe the decrease in 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibition, indicating that toxicity was due to parent molecules, and not to the formed metabolites. This is the first report of the isolation of bacterial strain able to transform two β-triketones.
在这项研究中，从先前用该除草剂处理过的土壤样本中分离到了一株能够将磺草酮（一种β-三酮除草剂）用作唯一碳源和能源的细菌菌株。基于 16S rRNA 基因序列的系统发育研究表明，该分离株与几种慢生根瘤菌具有 100%的相似度，因此被命名为慢生根瘤菌 SR1。质粒图谱显示，SR1 中存在一个大质粒（>50kb），在非选择性条件下不能被消除。通过电穿孔将其转移到大肠杆菌中未能诱导β-三酮降解能力，表明可能位于该质粒上的降解基因在大肠杆菌中无法表达，或者它们不是质粒携带的。评估 SR1 降解各种合成（mesotrione 和 tembotrione）和天然（leptospermone）三酮的能力表明，该菌株也能够降解 mesotrione。尽管 SR1 能够完全消除这两种除草剂，但磺草酮的降解速率是 mesotrione 的十倍，表明降解酶系统对磺草酮的亲和力更高。磺草酮的降解途径涉及到 2-氯-4-甲磺酰基苯甲酸（CMBA）的形成，该物质以前在磺草酮降解中被鉴定过，以及一个被鉴定为羟基磺草酮的新代谢物。mesotrione 的降解途径导致 4-甲基磺酰基-2-硝基苯甲酸（MNBA）和 2-氨基-4 甲基磺酰基苯甲酸（AMBA）的积累，这两种物质是该除草剂的两种已知代谢物。随着β-三酮的消散，可以观察到 4-羟基苯基丙酮酸双加氧酶（HPPD）抑制的降低，这表明毒性是由于母体分子，而不是形成的代谢物。这是首次报道分离出能够转化两种β-三酮的细菌菌株。
