Microbial Degradation of a Recalcitrant Pesticide: Chlordecone

Abstract

Chlordecone (Kepone®) is a synthetic organochlorine insecticide (C10Cl10O) used worldwide mostly during the 1970 and 1980s. Its intensive application in the French West Indies to control the banana black weevil Cosmopolites sordidus led to a massive environmental pollution. Persistence of chlordecone in soils and water for numerous decades even centuries causes global public health and socio-economic concerns. In order to investigate the biodegradability of chlordecone, microbial enrichment cultures from soils contaminated by chlordecone or other organochlorines and from sludge of a wastewater treatment plant have been conducted. Different experimental procedures including original microcosms were carried out anaerobically over long periods of time. GC-MS monitoring resulted in the detection of chlorinated derivatives in several cultures, consistent with chlordecone biotransformation. More interestingly, disappearance of chlordecone (50 μg/mL) in two bacterial consortia was concomitant with the accumulation of a major metabolite of formula C9Cl5H3 (named B1) as well as two minor metabolites C10Cl9HO (named A1) and C9Cl4H4 (named B3). Finally, we report the isolation and the complete genomic sequences of two new Citrobacter isolates, closely related to Citrobacter amalonaticus, and that were capable of reproducing chlordecone transformation. Further characterization of these Citrobacter strains should yield deeper insights into the mechanisms involved in this transformation process.

Natural Chlordecone Degradation Revealed by Numerous Transformation Products Characterized in Key French West Indies Environmental Compartments

“…Both early [34,35] and recent [36,37] studies of bacterial chlordecone degradation suggested two main TP families: hydrochlordecones from reductive dechlorination reactions (family A), and polychloroindenes formed after ring-opening and elimination steps (family B) (Figure 1).…”

“…Another study with the Archaeon Methanosarcina thermophila suggested quantitative chlordecone conversion into unknown polar and nonpolar metabolites based on silica gel thinlayer chromatography (TLC) [38]. The technique used for hydrochlordecones and polychloroindenes TP produced by consortium 86 [36] was applied here to confirm the uniqueness of TP formed during bacterial and archaeal chlordecone degradation. Retardation factor (Rf) values for polychloroindenes corresponded to those of nonpolar TP in Methanosarcina thermophila cultures [38], while hydrochlordecones behaved like chlordecone ( Figure S1).…”

“…Generally, POPs pollution is assessed and followed by environmental monitoring of the parent molecule, with restricted efforts dedicated to the possible TP in situ formed and their consequences as exemplified for aldrin. In the case of chlordecone, several bacterial degradation experiments suggested two main TP families evidenced by GC-MS [34,35] [36,37]. Despite extensive analytical studies on chlordecone contamination in the FWI [6], the only chlordecone derivatives hitherto detected in environmental samples, i.e.…”

Exploring biochemical diversity in bacteria

“…These compounds are all partially dechlorinated, but the mechanism(s) of dechlorination remain unknown. genome sequencing of the isolated species failed to identify known enzymes that catalyse any type of dechlorination, especially reductive (Chaussonnerie et al 2016).…”

Microbial degradation of pesticide: A review

“…Curiously they could identify organism was able to perform activity anaerobically at various range of temeperature throughout the year and the cbrA gene product; trichlorobenzene reductive dehalogenase was found to be more important enzyme. Chaussonnerie et al (2015) isolated and characterized two closely related species of Citrobacter amalonaticus those were able to transform recalcitrant chlordecone from pesticide contaminated soil. Endosulfan degradation by P. aeruginosa G1 (88.5%), Stenotrophomonas maltophilia G2 (85.5%), B. atrophaeus G3 (64.4%), Citrobacter amolonaticus G4 (56.7%) and Acinetobacter lowffii G5 (80.2%) was reported (Ozdal et al, 2016).…”