FIG. 4.

TOP52 ΔfimK and TOP52/pfimX have higher expression levels of type 1 pili than wild type and vector controls. FimA immunoblot analysis showed that TOP52 ΔfimK makes more type 1 pili than wild-type TOP52. Expression of FimA was complemented down to wild-type levels with pfimK. TOP52/pfimX also produced a much larger FimA band than the vector control. Bacteria were normalized by OD₆₀₀, and Coomassie blue staining was used to verify similar levels of protein in each lane. Relative densitometry was calculated using ImageJ software. Phase assays, showing the orientation of the fimS promoter region of the fim operon, revealed that the wild-type TOP52 and TOP52/pBAD vector control were largely phase OFF while TOP52 ΔfimK and TOP52/pfimX had significant phase-ON populations.