Organohalide Respiration with Diclofenac by Dehalogenimonas

Diclofenac (DCF) is a pharmaceutically active contaminant frequently found in aquatic ecosystems. The transformation pathways and microbiology involved in the biodegradation of DCF, particularly under anoxic conditions, remain poorly understood. Here, we demonstrated microbially mediated reductive dechlorination of DCF in anaerobic enrichment culture derived from contaminated river sediment. Over 90% of the initial 76.7 +/- 3.6 mu M DCF was dechlorinated at a maximum rate of 1.8 +/- 0.3 mu M day(-1) during a 160 days' incubation. Mass spectrometric analysis confirmed that 2-(2-((2-chlorophenyl)amino)phenyl)acetic acid (2-CPA) and 2anilinophenylacetic acid (2-APA) were formed as the monochlorinated and nonchlorinated DCF transformation products, respectively. A survey of microbial composition and Sanger sequencing revealed the enrichment and dominance of a new Dehalogenimonas population, designated as Dehalogenimonas sp. strain DCF, in the DCFdechlorinating community. Following the stoichiometric conversion of DCF to 2-CPA (76.0 +/- 2.1 mu M) and 2-APA (3.7 +/- 0.8 mu M), strain DCF cell densities increased by 24.4 +/- 4.4-fold with a growth yield of 9.0 +/- 0.1 x 10(8) cells per mu mol chloride released. Our findings expand the metabolic capability in the genus Dehalogenimonas and highlight the relevant roles of organohalide-respiring bacteria for the natural attenuation of halogenated contaminants of emerging concerns (e.g., DCF).

Automated summary

This study identified a anaerobic enrichment culture derived from contaminated river sediment that can mediate the reductive dechlorination of Diclofenac (DCF). It also discovered a new Dehalogenimonas population and highlighted the relevant roles of organohalide-respiring bacteria in the natural attenuation of halogenated contaminants.