title: Isolation and characterization of Bradyrhizobium sp. SR1 degrading two β-triketone herbicides.
abstract: 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.
authors.affiliation: 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.|INRA, UMR 1347 Agroécologie, Pole Ecoldur, 17 rue Sully, BP 86510, 21065, Dijon Cedex, France.
authors.forename: Sana
authors.initials: S
authors.lastname: Romdhane
authors.affiliation: INRA, UMR 1347 Agroécologie, Pole Ecoldur, 17 rue Sully, BP 86510, 21065, Dijon Cedex, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Devers-Lamrani
authors.affiliation: INRA, UMR 1347 Agroécologie, Pole Ecoldur, 17 rue Sully, BP 86510, 21065, Dijon Cedex, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Martin-Laurent
authors.affiliation: Laboratoire de Chimie des Biomolécules et de l'Environnement-CRIOBE-USR 3278 CNRS EPHE, University of Perpignan Via Domitia, 66860, Perpignan, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Calvayrac
authors.affiliation: Biocapteurs Analyses Environnement (BAE), University of Perpignan Via Domitia, 66860, Perpignan, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Rocaboy-Faquet
authors.affiliation: INPT, ENSIACET, Université de Toulouse, 31432, Toulouse, France.|Laboratoire de Génie Chimique (LGC UMR 5503), CNRS, 4 allée Emile Monso, BP 84234, 31432, Toulouse, France.
authors.forename: David
authors.initials: D
authors.lastname: Riboul
authors.affiliation: Laboratoire de Chimie des Biomolécules et de l'Environnement-CRIOBE-USR 3278 CNRS EPHE, University of Perpignan Via Domitia, 66860, Perpignan, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Cooper
authors.affiliation: Biocapteurs Analyses Environnement (BAE), University of Perpignan Via Domitia, 66860, Perpignan, France. barthelm@univ-perp.fr.
authors.forename: Lise
authors.initials: L
authors.lastname: Barthelmebs
mesh_terms: D015111:4-Hydroxyphenylpyruvate Dioxygenase / Q000037:antagonists & inhibitors; D020369:Bradyrhizobium / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003512:Cyclohexanones / Q000378:metabolism* / Q000633:toxicity; D004926:Escherichia coli; D006540:Herbicides / Q000378:metabolism*; D008698:Mesylates / Q000378:metabolism* / Q000633:toxicity; D010802:Phylogeny; D012988:Soil Microbiology
chemical_list: D003512:Cyclohexanones; D006540:Herbicides; D008698:Mesylates; C079906:sulcotrione; D015111:4-Hydroxyphenylpyruvate Dioxygenase
keywords: Biodegradation; Bradyrhizobium sp. SR1; Mesotrione; Sulcotrione; β-Triketone