Research on novel degradation enzymes and genes essential to microbial degradation of persistent chlorinated organophosphorus triesters

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The chlorinated organophosphorus(OP) compounds tris(2-chloroethyl) phosphate(TCEP) and tris(1, 3-dichloro-2-propyl) phosphate(TDCPP) are widely used as flame retardants mainly in a range of plastic foams, resins, and latexes and in the production of liquid unsaturated polyester resins, respectively. They are hard to eliminate not only in the environment but also in sewage treatment plants. Many studies have shown several toxic effects of the compoundsIn this study, novel bacteria degrading trihaloalkyl phosphates, Sphingomonas sp. strain TDK1 and Sphingobium sp. strain TCM1, were isolated from soil by growth on TDCPP or TCEP as a sole phosphorus source, respectively. The two strains were able to degrade and assimilate not only the chlorinated OP flame retardants but also several other OP flame retardants and plasticizers, and the strains possessed different substrate specificity for trialkyl phosphates. We purified and characterized phosphotriesterases, catalyzing the first step of TCEP and TDCPP degradation, from Sphingobium sp. TCM1 and Sphingomonas sp. TDK1, respectively. The corresponding genes of the enzymes were cloned and analyzed. The results suggested that both the enzymes were very closely related each other and very distantly related to phosphotriesterases so far reported.