Catabolism of 4-hydroxy- and 4,4'-dihydroxydiphenyl ether by Sphingomonas sp. strain SS3 leads to the production of a toxic metabolite

Abstract

The diphenyl ether degrading bacterial strain Sphingomonas sp. SS3, although not able to utilize 4-hydroxy- and 4,4'-dihydroxydiphenyl ether as sole sources of carbon and energy, is nevertheless capable of transforming these diaryl ethers into mononuclear hydroxylated aromatic compounds. The cleavage of the ether-bridge is prompted by an angular dioxygenation, yielding an unstable hemiacetal which spontaneously decays into catechol, phenol, 1,4-dihydroxy- and 1,2,4-trihydroxybenzene in the case of 4-hydroxydiphenyl ether, and 1,4-dihydroxy- and 1,2,4-trihydroxybenzene in the case of 4,4'-dihydroxydiphenyl ether, respectively. Although catechol and phenol are utilized as carbon sources, 1,4-dihydroxy- and 1,2,4-trihydroxybenzene are not. The 1,2,4-trihydroxybenzene proved able to inhibit growth of Sphingomonas sp. strain SS3, probably explaining why this organism is not able to grow at the expense of these p-hydroxylated diphenyl ethers.