title: Formation of 2,4-D bound residues in soils: New insights into microbial metabolism.
abstract: The microbial contribution to the formation of bound residues in soils is studied by characterizing the metabolic activity of three microorganisms (Trametes versicolor, Fusarium solani and Ralstonia eutropha) on14C-2,4-dichlorophenoxyacetic acid (2,4-D) during incubation in synthetic liquid media and soil. A fractionation protocol was applied to quantify the14C-2,4-D that was incorporated into the biomass among biomolecular-like fractions. Successive fractionation of microbial biomass was implemented to break up and quantify the methanol/dichloromethane fraction (corresponding to the14C-lipid-like fraction), the trichloroacetic acid fraction (or hydrolysed14C-polysaccharide-like fraction) and the acid hydrolysable fraction (or the hydrolysed14C-protein-like fraction). Relevant differences in the 2,4-D degradation and biomass radioactivity distribution among the three microorganisms were found. The14C-protein-like fraction was the most consistent biomass fraction for reflecting the pesticide use capacity of the microorganisms under liquid and soil conditions. 2,4-D and its metabolite 4-chlorophenol were detected in methanol/dichloromethane and trichloroacetic acid fractions of the biomass of microorganisms exhibiting a low capacity to mineralize 2,4-D, thus proving that the microbial participation in the formation of bound residues while conserving the initial pesticide structure under natural soil conditions may be intimately associated with the lipid- and polysaccharide-like constituents. The fractionation protocol differentiates between14C that is incorporated into biomass as a biomolecular constituent and the pesticide or its metabolites that accumulate in the biomass and thus correspond to the stricto sensu definition of bound residues.
authors.affiliation: Grupo de Investigaciones y Mediciones Ambientales, Universidad de Medellín, Carrera 87 No. 30-65, Medellín, Colombia.
authors.forename: Liliana Rocío
authors.initials: LR
authors.lastname: Botero
authors.affiliation: UMR ECOSYS, INRA, AgroParisTech, Université Paris-Saclay, 78026 Versailles, France.
authors.forename: Chistian
authors.initials: C
authors.lastname: Mougin
authors.affiliation: Grupo Diagnóstico y Control de la Contaminación, Sede de Investigación Universitaria, Universidad de Antioquia, Calle 62 No. 52-59, Medellín, Colombia.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Peñuela
authors.affiliation: UMR ECOSYS, INRA, AgroParisTech, Université Paris-Saclay, 78850 Thiverval-Grignon, France. Electronic address: enrique.barriuso@inra.fr.
authors.forename: Enrique
authors.initials: E
authors.lastname: Barriuso
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000032:analysis*; D018533:Biomass; D005670:Fusarium / Q000378:metabolism; D006540:Herbicides / Q000032:analysis*; D043367:Ralstonia / Q000378:metabolism; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis*; D055454:Trametes / Q000378:metabolism
chemical_list: D006540:Herbicides; D012987:Soil; D012989:Soil Pollutants; D015084:2,4-Dichlorophenoxyacetic Acid
keywords: 2,4-D; Biodegradation; Bound residues; Pesticides; Soil