Bacterial metabolism of 2,4-dichlorophenoxyacetate

Abstract

1. Two Pseudomonas strains isolated from soil metabolized 2,4-dichlorophenoxyacetate (2,4-D) as sole carbon source in mineral salts liquid medium. 2. 2,4-Dichlorophenoxyacetate cultures of Pseudomonas I (Smith, 1954) contained 2,4-dichlorophenol, 2-chlorophenol, 3,5-dichlorocatechol and α-chloromuconate, the last as a major metabolite. 3. Dechlorination at the 4(p)-position of the aromatic ring must therefore take place at some stages before ring fission. 4. Pseudomonas N.C.I.B. 9340 (Gaunt, 1962) cultures metabolizing 2,4-dichlorophenoxyacetate contained 2,4-dichloro-6-hydroxyphenoxyacetate, 2,4-dichlorophenol, 3,5-dichlorocatechol and an unstable compound, probably αγ-dichloromuconate. 5. Cell-free extracts of the latter organism grown in 2,4-dichlorophenoxyacetate cultures contained an oxygenase that converted 3,5-dichlorocatechol into αγ-dichloromuconate, a chlorolactonase that in the presence of Mn²⁺ ions converted the dichloromuconate into γ-carboxymethylene-α-chloro-Δ^αβ-butenolide, and a delactonizing enzyme that gave α-chloromaleylacetate from this lactone. 6. Pathways of metabolism of 2,4-dichlorophenoxyacetate are discussed.