Microbial community of a chlordecone contaminated nitisol subject to a remediation process based on chemical reduction. Microbial community of a chlordecone contaminated nitisol subject to a remediation process based on chemical reduction

The intensive application of the insecticide chlordecone (CLD) in the French West Indies (FWI) led to widespread environmental pollution and major threats to living organisms. To test one possible remediation process, a previous laboratory pilot-scale experiment was conducted with a CLD-contaminated nitisol amended with Daramend® (reduced iron mixed with plant material) and subjected to sequential reducing/oxidizing phases. The present study provides a thorough insight into the microbial community of the control and treated mesocosms during the course of the 6-month remediation process. The soil treatment resulted in changes in the abundance, structure and diversity of the microbial community. The predominance of both bacterial and fungal groups known to be stimulated in C-rich environments and to play roles in the intermediary metabolism of organic matter were observed in the treated soil. Nitrate-, iron- and sulfate-reducers were stimulated during the treatment, possibly contributing to a biotic CLD transformation. Quite interestingly, the soil treatment resulted also in the enrichment of some known dechlorinating microorganisms, mostly the non-obligate organohalide-respiring bacteria Anaeromyxobacter dehalogenans. The actual role of these microorganisms in the transformation of CLD remains to be characterized, notably because they constitute a candidate dechlorinating reservoir for degradation of dechlorinated CLD-transformation products formed by the chemical reduction pathway.