Fig 3.

Relative GFP fluorescence of flagellar mutant strains of P. syringae B728a harboring either a plasmid in which GFP expression is dependent on the promoter of rhlA (A) or on the promoter of fliC (B). Promoter strains were inoculated at a range of 10⁵ to 10⁷ cells in 5-μl suspensions onto agar plates and incubated for 20 h to yield a range of cell densities at the time of sampling. The error bars represent the standard deviations of the mean cell-normalized GFP fluorescence. Promoter expression was significantly different in the mutant strain compared to the ΔsyfA strain at the highest cell density at a confidence level of P < 0.05 (∗) or P < 0.01 (∗∗) as determined by a t test.