Bacterial metabolism of 4-chlorophenoxyacetate

Abstract

1. A pseudomonad capable of utilizing 4-chlorophenoxyacetate (CPA) as sole source of organic carbon was isolated from soil. 2. The organism was grown in liquid culture and the following compounds were isolated and identified in culture extracts: 4-chloro-2-hydroxyphenoxyacetate, 4-chlorocatechol, β-chloromuconate probably the cis–trans isomer and γ-carboxymethylene-Δαβ-butenolide. 3. Cells grown on 4-chlorophenoxyacetate were able to metabolize 4-chloro-2-hydroxyphenoxyacetate, 4-chlorocatechol and γ-carboxymethylene-Δαβ-butenolide without a lag period. They were not adapted to 4-chlorophenol, or to either culture isolated or synthetic β-chloromuconate, possibly because of stereospecificity towards the cis–cis isomer. 4. On the basis of isolation and induction evidence, the following metabolic pathway is proposed for the breakdown of 4-chlorophenoxyacetate by this organism: 4-chlorophenoxyacetate → 4-chloro-2-hydroxyphenoxyacetate → 4-chlorocatechol → cis–cis-β-chloromuconate → γ-carboxymethylene-Δαβ-butenolide → maleylacetate and fumarylacetate → fumarate and acetate.