FIG 5.

Influence of the nuh promoter mutation on nuh expression. (Top) The promoter mutation (var) was found in variants A and B. Shown are the LasR binding site (36), the predicted −10 and −35 sequences, the E. coli consensus (white text) (50, 51), and the ATG start codon. The transcription start site has not been experimentally resolved (66). (Bottom) We used a nuh-gfp fusion to measure transcriptional activation from the wild-type and variant promoters. Data are presented as total fluorescence divided by OD₆₀₀. In the absence of LasR, GFP was below the limit of detection from the wild-type promoter. Expression of the variant promoter in a LasR⁻ mutant resulted in a 4.5-fold increase in GFP compared to the wild-type promoter in PAO1. In PAO1, the variant promoter was associated with an 18.5-fold increase in GFP compared to the wild-type promoter sequence. All pairwise comparisons are statistically significant using a t test (P < 0.001 in all cases).