Identification of a meta-cleavage pathway for metabolism of phenoxyacetic acid and phenol in pseudomonas-cepacia AC1100

Abstract

Pseudomonas cepacia strain AC1100 grows luxuriantly on 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) but does not utilize phenoxyacetic acid. After long-term selective pressure on phenoxyacetic acid, mutants designated as strain PAA, capable of utilizing phenoxyacetic acid as well as phenol, emerged spontaneously at a frequency of 1X10(-8). A deletion mutant strain PT88, which is devoid of a part of 2,4,5-T metabolic pathway. generated neither phenoxyacetic acid utilizing nor phenol-utilizing mutants. The wild type (Wt) strain AC1100 and all its mutants utilized benzoate via ortho-cleavage pathway. However, only mutant strain PAA harbored the whole set of enzymes required for utilization of phenol via meta-cleavage pathway. The results suggest that wt strain AC1100 carries silent genes for meta-cleavage pathway which are expressed in strain PAA enabling it to utilize phenoxyacetic acid and phenol. Gene activation is presumed to he due to the translocation of insertion elements.