Figure 4. YbjN suppresses bacterial motility and over-expression of ybjN negatively regulates flagellar gene expression.

A. Migration phenotypes of E. coli strain BW25113 (BW), ybjN mutant and BW over-expressing ybjN at12 h after incubation. B. Comparison of the movement distance of BW, ybjN and BW over-expressing ybjN. Cells were inoculated on the surface of a motility plate containing 0.25% agar as described previously [20]. Plates were incubated at 30°C for 24 h, during which the displacement (diameter) of the outermost edge of the movement was measured. The experiment was performed for three times in triplicate. Errors bars were smaller than the symbols. C. Relative expression of fliA and flgD gene expression in ybjN mutant and BW over-expressing ybjN compared to BW strain. Bacterial strains were grown overnight in LB broth and re-inoculated in 5 mL M9 medium. Relative expression of fliA and flgD genes, normalized to the expression value of 16S rRNA (rrsA) gene, was determined by qRT-PCR after 8 h growth (OD₆₀₀ at 0.5–0.8) in M9 medium.