PHENOLS AS INTERMEDIATES IN THE DECOMPOSITION OF PHENOXYACETATES BY AN ARTHROBACTER SPECIES

Abstract

Decomposition of 2,4-dichlorophenoxyacetate (2,4-D) by a soil arthrobacter was studied using the technique of sequential induction. Compounds oxidized rapidly and without a lag by 2,4-D-grown cells, but slowly or not at all by citrate-grown cells, included 2,4-D, 2- and 4-chlorophenoxyacetate, 3,5-dichloro- and 4-chloro-catechol, catechol, 2,4-dichlorophenol, and 2- and 4-chlorophenol. The manometric data suggested that phenols and catechols were intermediates in the degradation of phenoxyacetates. Resting cells failed to accumulate chlorine-substituted phenols during the metabolism of halogenated phenoxyacetates, apparently because the phenols were oxidized as readily as they were formed. However, 2,4-D-induced cells contained enzymes which acted upon phenoxyacetate and 4-hydroxyphenoxyacetate, but these cells did not metabolize phenol and hydroquinone. Suspensions of such bacteria, but not citrate-grown cells, converted phenoxyacetate and 4-hydroxyphenoxyacetate almost completely to phenol and hydroquinone, respectively. The results indicate that the Arthrobacter sp. degrades 2,4-D via 2,4-dichlorophenol, and 2- and 4-chlorophenoxyacetate via 2- and 4-chlorophenol, respectively. The results also demonstrate a new technique for obtaining high yields of an intermediate in a metabolic sequence.