Role of the uvr gene in the SOS function inducing activity of two tryptophan pyrolysis products, Trp-P-1 and Trp-P-2, in Escherichia coli K12

Abstract

Two tryptophan pyrolysis products, Trp-P-1 and Trp-P-2 were assayed in the SOS-chromotest using PQ 37 ( uvr A) and PQ 35 ( uvr +) E. coli K12 strains, in the presence of S9 fraction from Aroclor-induced rats. Both compounds were able to induce the expression of SOS functions in uvr A bacteria, in the following order: Trp-P-1 < Trp-P-2 < aflatoxin B1, at low concentrations (<125 ng/assay). In this range, the induction of SOS functions was significantly decreased in the uvr + strain. This implies that the uvr gene product plays an important role in the repair of genotoxic damage induced by Trp-P-1 and Trp-P-2. At higher concentrations (125–500 ng/assay), Trp-P-1 became more efficient in inducing SOS functions than Trp-P-2 and excision repair was less efficient than at low concentration.