Isolation and characterisation of a bacterial strain degrading the herbicide sulcotrione from an agricultural soil

Laboratoire de Chimie des Biomolécules et de l'Environnement, Université de Perpignan Via Domitia, Perpignan, France.
Pest Management Science (Impact Factor: 2.74). 03/2012; 68(3):340-7. DOI: 10.1002/ps.2263
Source: PubMed

ABSTRACT The dissipation kinetics of the herbicide sulcotrione sprayed 4 times on a French soil was studied using a laboratory microcosm approach. An advanced cultivation-based method was then used to isolate the bacteria responsible for biotransformation of sulcotrione. Chromatographic methods were employed as complementary tools to define its metabolic pathway.
Soil microflora was able quickly to biotransform the herbicide (DT(50) ≈ 8 days). 2-Chloro-4-mesylbenzoic acid, one of its main metabolites, was clearly detected. However, no accelerated biodegradation process was observed. Eight pure sulcotrione-resistant strains were isolated, but only one (1OP) was capable of degrading this herbicide with a relatively high efficiency and to use it as a sole source of carbon and energy. In parallel, another sulcotrione-resistant strain (1TRANS) was shown to be incapable of degrading the herbicide. Amplified ribosomal restriction analysis (ARDRA) and repetitive extragenic palendromic PCR genomic (REP-PCR) fingerprinting of strains 1OP and 1TRANS gave indistinguishable profiles.
Sequencing and aligning analysis of 16S rDNA genes of each pure strain revealed identical sequences and a close phylogenetic relationship (99% sequence identity) to Pseudomonas putida. Such physiological and genetic properties of 1OP to metabolise sulcotrione were probably governed by mobile genetic elements in the genome of the bacteria.

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Available from: Christophe Calvayrac, Apr 22, 2014
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    • "Sulcotrione degradation in the soil is influenced by biotic and/or abiotic factors [3]. Half-life ranges between 45 and 65 days in soil and is 8 days with microflora [2]. 1,3- Cyclohexanedione (CHD) and 2-chloro-4-mesylbenzoic acid (CMBA) are among the observed degradation compounds [10]. "
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    • "The amount of b-triketone herbicides (sulcotrione or tembotrione ) and, concomitantly, the amount of the main metabolites of sulcotrione, CHD and CMBA (Calvayrac et al., 2012) remaining in the extra-cellular medium of bacterial cultures were measured by chromatographic methods during the time-course of the biodegradation process. Culture media extracts were prepared according to the procedure already described by the authors (Calvayrac et al., 2012 "
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    ABSTRACT: Pseudomonas sp. 1OP, previously isolated from a French agricultural soil, has been described as the first sulcotrione degrading bacteria. Different conditions of initial pH and herbicide concentration in liquid culture were tested to evaluate the growth performances of the isolate and its degrading capacity, with sulcotrione as the sole carbon and/or energy source. Maximal growth rate (μmax) was obtained under initial neutral conditions and with initial concentration of sulcotrione close to 180 μM, and was described, during the exponential phase, by a sigmoidal curve which could be easily fitted to the modified Gompertz equation. Complementary studies carried on the CMBA by-product and on another β-triketone herbicide showed the relative specificity of the strain against sulcotrione. The sulcotrione degrading phenotype of Pseudomonas sp.1OP was shown to be lost under non-selective conditions. Plasmid-Eckardt modified method, consecutively applied for plasmid profiling, showed that this strain carries one large plasmid (>12 kb) bearing putative genes involved in sulcotrione degradation, as demonstrated by curing experiment.
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    • "At pH 5, amounts of SCMBA (up to 12% of initial sulcotrione after 60 min irradiation) were found, a value significantly higher than TCMBA, under the same conditions. Therefore, the route leading to SCMBA and CHD, generally described as a biotic environmental degradation pathway (Calvayrac et al., 2012; Chaabane et al., 2005, 2008; Cherrier et al., 2005; Rouchaud et al., 1996, 1998a, 1998b), seems to occur as a minor mechanism during the photolysis process. "
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