FIG 3 .

ICP-MS analysis of total cellular zinc content in S. Typhimurium following NO· treatment and transcriptional monitoring of NO· sensed by cells. (A) S. Typhimurium cells at an OD₆₀₀ of ≈1 were treated with 2 mM diethylamine NONOate (DEANO), and total cellular zinc was measured at various times posttreatment. By 5 min posttreatment, total cellular zinc had fallen significantly compared to untreated cells, suggesting that zinc is effluxed from the cell following NO· treatment. Zinc levels gradually recovered to baseline levels over the course of 60 min. Statistical significance was determined by unpaired two-tailed t test; * indicates P values of <0.001 and 0.036, respectively. Error bars represent standard deviations. (B) A portion of each culture at each time point was also used to prepare RNA and cDNA for transcriptional analysis. Data are presented as the mean fold change in transcript level compared to untreated cells at each time point. The error bars represent standard deviations. Expression of hmp is regulated by the NO·-sensing NsrR regulator. The high level of expression at 5 min posttreatment indicates that the highest levels of NO· were present during this time period. At later time points, the level of hmp transcript declined significantly, indicating that the amount of NO· declined by 15 min posttreatment and remained low thereafter.