Identification of sulfonylurea biodegradation pathways enabled by a novel nicosulfuron-transforming strain Pseudomonas fluorescens SG-1: Toxicity assessment and effect of formulation.
Nicosulfuron is a selective herbicide belonging to the sulfonylurea family, commonly used on maize culture. A bacterial strain SG-1 was isolated from an agricultural soil previously treated with nicosulfuron. This strain was identified as Pseudomonas fluorescens and is able to quantitatively dissipate 77.5% of nicosulfuron (1mM) at 28°C in the presence of glucose within the first day of incubation. Four metabolites were identified among which ASDM (2-(aminosulfonyl)-N,N-dimethyl-3-pyridinecarboxamide) and ADMP (2-amino-4,6-dimethoxypyrimidine) in substantial proportions, corresponding to the hydrolytic sulfonylurea cleavage. Two-phase dissipation kinetics of nicosulfuron by SG-1 were observed at the highest concentrations tested (0.5 and 1mM) due to biosorption. The extend and rate of formulated nicosulfuron transformation were considerably reduced compared to those with the pure active ingredient (appearance of a lag phase, 30% dissipation after 10days of incubation instead of 100% with the pure herbicide) but the same metabolites were observed. The toxicity of metabolites (standardized Microtox®test) showed a 20-fold higher toxicity of ADMP than nicosulfuron. P. fluorescens strain SG-1 was also able to biotransform two other sulfonylureas (metsulfuron-methyl and tribenuron-methyl) with various novel pathways. These results provide new tools for a comprehensive picture of the sulfonylurea environmental fate and toxicity of nicosulfuron in the environment.
Clermont Université, Université Blaise Pascal, F-63000 Clermont-Ferrand, France; CNRS, UMR 6023, Laboratoire Microorganismes: Génome et Environnement, TSA 60026, CS 60026, 63178 Aubière Cedex, France; CNRS, UMR 6296, Institut de Chimie de Clermont-Ferrand, TSA 60026, CS 60026, 63178 Aubière Cedex, France.
Louis
L
Carles
Clermont Université, Université Blaise Pascal, F-63000 Clermont-Ferrand, France; CNRS, UMR 6023, Laboratoire Microorganismes: Génome et Environnement, TSA 60026, CS 60026, 63178 Aubière Cedex, France.
Muriel
M
Joly
Clermont Université, Université Blaise Pascal, F-63000 Clermont-Ferrand, France; CNRS, UMR 6023, Laboratoire Microorganismes: Génome et Environnement, TSA 60026, CS 60026, 63178 Aubière Cedex, France.
Frédérique
F
Bonnemoy
Clermont Université, Université Blaise Pascal, F-63000 Clermont-Ferrand, France; CNRS, UMR 6296, Institut de Chimie de Clermont-Ferrand, TSA 60026, CS 60026, 63178 Aubière Cedex, France.
Martin
M
Leremboure
Clermont Université, Université Blaise Pascal, F-63000 Clermont-Ferrand, France; CNRS, UMR 6023, Laboratoire Microorganismes: Génome et Environnement, TSA 60026, CS 60026, 63178 Aubière Cedex, France. Electronic address: isabelle.batisson@univ-bpclermont.fr.
Isabelle
I
Batisson
Clermont Université, Université Blaise Pascal, F-63000 Clermont-Ferrand, France; CNRS, UMR 6296, Institut de Chimie de Clermont-Ferrand, TSA 60026, CS 60026, 63178 Aubière Cedex, France. Electronic address: pascale.besse@univ-bpclermont.fr.
Pascale
P
Besse-Hoggan
D001673:Biodegradation, Environmental; D001711:Biotransformation; D006540:Herbicides / Q000378:metabolism* / Q000633:toxicity; D007700:Kinetics; D011551:Pseudomonas fluorescens / Q000187:drug effects / Q000378:metabolism*; D011725:Pyridines / Q000378:metabolism* / Q000633:toxicity; D013453:Sulfonylurea Compounds / Q000378:metabolism* / Q000633:toxicity
D006540:Herbicides; D011725:Pyridines; D013453:Sulfonylurea Compounds; C416723:nicosulfuron
Metabolite; Metsulfuron-methyl; Microtox(®); Nicosulfuron; Tribenuron-methyl