FIG 8.

Phase-variable expression of either FljB or FliC is controlled in part by the inversion of the fljB-fljA promoter region. Endpoint PCR using primers designed to flank the Hin-invertible promoter region upstream of fljB-fljA was conducted, and the resultant product sizes (lower right) enabled determination of fljB-fljA-ON (fliC-OFF) or fljB-fljA-OFF (fliC-ON) promoter orientation. The genomic DNA template was normalized prior to 15 cycles of PCR amplification of the fljB-fljA promoter region or rpoB (bottom).