Induction of umuC gene expression by nitrogen dioxide in Salmonella typhimurium.

Abstract Gaseous nitrogen dioxide (NO 2 ) was found to induce umuC gene expression in Salmonella typhimurium carrying the umuC-lacZ fusion plasmid. The induction level of the umu operon responsible for inducible mutagenesis was measured by the level of β-galactosidase in the cell, encoded by the fusion gene. NO 2 gas was bubbled into bacterial suspensions at 10, 30 and 90 μl/l for 30 min at a flow rate of 100 ml/min. Expression of the umuC gene varied with the concentration, flow rate and bubbling time of the NO 2 gas. Although NO 2 gas induces SOS functions, mutagenesis due to it was not detectable in Salmonella typhimurium TA100 and TA102. Nitric oxide gas (NO) did not induce any umuC gene expression.