FIG 3.

Expression of the different nrd genes depends on cell interaction. mRNA levels of the nrdR, nrdAp, nrdAc, nrdD, and nrdE genes in associated bacteria (after a 3-h, 8-h, or 24-h infection period) relative to those of AIEC LF82 bacteria grown during similar periods in MEM cell culture medium were compared using quantitative RT-PCR. As controls, 16S rRNA levels were measured. Results are expressed as the number of mRNA-encoding nrd genes for 10⁷ copies of mRNA-encoding 16S rRNA. Only experiments that demonstrated the same levels of 16S rRNA for each sample were taken into account. The data represent the means from at least three separate experiments, and the bars represent the SEM.