Expression of the class 3 fliD and motA genes in the spiC mutant. Bacteria were cultured in LB to an OD600 of 1.6, and the total RNA was extracted from the wild-type Salmonella (WT), spiC mutant strain, or spiC mutant strain carrying the spiC gene-containing plasmid pEG9127 (spiC+). Quantitative RT-PCR was conducted using a TaqMan probe. Levels of fliD (A) or motA (B) mRNA were normalized to 16S rRNA levels, and the results are shown relative to the expression in the wild-type strain. The expression levels of both genes in the spiC mutant were greatly reduced compared to the wild-type strain.