Anaerobic Degradation of Dicamba via a Novel Catabolic Pathway by a Consortium Enriched from Deep Paddy Soil

Dicamba is widely used in the paddy field to control broadleaf weeds. Dicamba easily migrates to deep soil, which is anoxic; however, the anaerobic catabolism of dicamba in paddy soil is still unknown. In this study, an anaerobic dicamba-degrading consortium was enriched from deep paddy soil. The consortium completely degraded 0.83 mM dicamba within 7 days. Five metabolites were identified, one of which is a new metabolite, 2,5-dichlorophenol, and a novel anaerobic dicamba degradation pathway was proposed. 2.5 mM dicamba, 1.5-2.0% NaCl, and 20 mM electron acceptors Na₂SO₄, NaNO₃, and FeCl₃, and 0.5 mM or more of metabolites 3-CP and 2,5-DCP strongly inhibited the degradation efficiency. During enrichment, the microbial community of the consortium was significantly changed with OTU numbers, and diversity decreased. The study is valuable to elucidate the catabolism and ecotoxicology studies of dicamba in paddy soil and to facilitate the engineering application of anaerobic technology to treat dicamba-manufacturing wastewater.