FIG. 2.

Repression of mntH transcription by transition metals. Wild-type reporter strain MM2507 (S. enterica serovar Typhimurium SL1344 bearing plasmid pMLZ104) was grown aerobically overnight at 37°C in M9-0.2% glucose-50 μg of ampicillin/ml containing the sulfate or chloride salts of various divalent first-row transition metals at a concentration of 10 or 100 μM as indicated. The β-galactosidase activity of saturated cultures (OD₆₀₀ of 1.0 to 1.5 ) was normalized to that of a culture containing no added metal (about 300 Miller units). Results represent the means and standard errors of two to five independent experiments in each case.