A metagenomic approach to the identification of UDP-glucose 4-epimerase as a menadione resistance protein.

Quinones are potentially toxic agents that generate reactive oxygen species (ROS) upon reduction. We screened a metagenomic library for a menadione resistance gene to identify UDP-glucose 4-epimerase (UGE). Escherichia coli carrying the gene became resistant to various quinones, but not to ROS. Because UGE is involved in the biosynthesis of lipopolysaccharides, it may have contributed to forming a permeability barrier against lipophilic quinones.