Fig 4.

Effects of single point mutations on ctxAB transcription. β-Galactosidase results from ctxAB::lacZ single point mutations are shown. Results for full-length WT and truncated WT (pJW211) promoter constructs are shown at the far left. Individual mutation results correlate with the nucleotide underneath the x axis. Heptad repeats included for mutagenesis are numbered and indicated by dotted arrows; imperfect repeat 7 is illustrated by a dashed arrow. Black bars are O395 WT toxT strains, and white bars are O395 ΔtoxT strains. The asterisks indicate statistically significant differences in β-galactosidase results between O395 WT toxT PctxAB and O395 ΔtoxT PctxAB strains according to Student's t test (P < 0.03).