Dehalococcoides-Containing Enrichment Cultures Transform Two Chlorinated Organophosphate Esters

Abstract

Although chlorinated organophosphate esters (Cl-OPEs) have been reported to be ubiquitously distributed in various anoxic environments, little information is available on their fate under anoxic conditions. In this study, we report two Dehalococcoides-containing enrichment cultures that transformed 3.88 ± 0.22 μmol tris(2-chloroethyl) phosphate (TCEP) and 2.61 ± 0.02 μmol tris(1-chloro-2-propyl) phosphate (TCPP) within 10 days. Based on the identification of the transformed products and deuteration experiments, we inferred that TCEP may be transformed to generate bis(2-chloroethyl) phosphate and ethene via one-electron transfer (radical mechanism), followed by C−O bond cleavage. Ethene was subsequently reduced to ethane. Similarly, TCPP was transformed to form bis(1-chloro-2-propyl) phosphate and propene. 16S rRNA gene amplicon sequencing and quantitative polymerase chain reaction analysis revealed that Dehalococcoides was the predominant contributor to the transformation of TCEP and TCPP. Two draft genomes of Dehalococcoides assembled from the metagenomes of the TCEP-and TCPP-transforming enrichment cultures contained 14 and 15 putative reductive dehalogenase (rdh) genes, respectively. Most of these rdh genes were actively transcribed, suggesting that they might contribute to the transformation of TCEP and TCPP. Taken together, this study provides insights into the role of Dehalococcoides during the transformation of representative Cl-OPEs.

Source Identification of Organophosphate Esters through the Profiles in Proglacial and Ocean Sediments from Ny-Ålesund, the Arctic

“…This was also supported by the evidence that the concentrations of DNBP, BEHP, DEP, BBOEP, and DOTP in proglacial sediments (15–112 pg/g dw, Table S6) were higher than those in ocean sediments (ND-95 pg/g dw). In addition to photodegradation, microbial degradation of tri-OPEs might be another important source of di-OPEs in sediments. , The half-lives of TPhP, TCIPP, TNBP, and TOTP in sediments ranged from 78 to 542 days (Table S1) and were much longer than their photodegradation half-lives (0.14–20 d). This indicated that the efficiency of microbial degradation of tri-OPEs in sediments might be lower than the efficiency of photodegradation.…”

“…In addition to photodegradation, microbial degradation of tri-OPEs might be another important source of di-OPEs in sediments. 15,16 The half-lives of TPhP, TCIPP, TNBP, and TOTP in sediments ranged from 78 to 542 days (Table S1) and were much longer than their photodegradation half-lives (0.14−20 d). This indicated that the efficiency of microbial degradation of tri-OPEs in sediments might be lower than the efficiency of photodegradation.…”

“…Tri-OPEs can react with hydroxyl radicals or ozone radicals under ultraviolet radiation in the atmosphere, forming the corresponding di-OPEs . Di-OPEs can also be produced by oxidative dealkylation of tri-OPEs in organisms (including microorganisms). , Currently, di-OPEs have been detected in the global atmosphere and fishmeal. , Some studies have suggested that the toxicity of certain di-OPEs may be higher than that of their corresponding parent tri-OPEs. For example, bis-(1-chloro-2-propyl) phosphate (BCIPP), bis­(1,3-dichloro isopropyl) phosphate (BDCIPP), and diphenyl phosphate (DPhP) have higher estrogen-disrupting and mineralocorticoid-disrupting potential than those of their corresponding parent tri-OPEs .…”

“…14 Di-OPEs can also be produced by oxidative dealkylation of tri-OPEs in organisms (including microorganisms). 15,16 Currently, di-OPEs have been detected in the global atmosphere and fishmeal. 17,18 Some studies have suggested that the toxicity of certain di-OPEs may be higher than that of their corresponding parent tri-OPEs.…”

Organophosphate Esters (OPEs) Flame Retardants in Water: A Review of Photocatalysis, Adsorption, and Biological Degradation

“…The main products of ultrasonic treatment TCEP were monoester and diester. Zhu et al [ 44 ] reported two enriched cultures containing dehalococcoides that transformed TCPP and TCEP within 10 days. The results deduced that TCEP might be converted to di (2-chloroethyl) phosphate and ethylene based on the identification of the conversion products and deuteration experiments by radical mechanism followed by C–O bond cleavage.…”