Induction of the soxRS regulon of Escherichia coli by glycolaldehyde

The ability of short-chain sugars to cause oxidative stress has been examined using glycolaldehyde as the simplest sugar. Short-chain sugars autoxidize in air, producing superoxide and α,β-dicarbonyls. In Escherichia coli the soxRS regulon mediates an oxidative stress response, which protects the cell against both superoxide-generating agents and nitric oxide. In superoxide dismutase-deficient E. coli mutants, glycolaldehyde induces fumarase C and nitroreductase A, which are regulated as members of the soxRS regulon. A mutational defect in soxRS eliminates that induction. This establishes that glycolaldehyde can cause induction of this defensive regulon. This effect of glycolaldehyde was oxygen-dependent, was not shown by glyoxal, and was not seen in the superoxide dismutase-replete parental strain, and it was abolished by a cell-permeable SOD mimetic. All of these suggest that superoxide radicals produced by the oxidation of glycolaldehyde played a key role in the induction.