Growth curves.

RW1 and RW1 constructs were incubated overnight on LB agar with the appropriate antibiotic at 30°C. LB broth (50 ml) was inoculated with a loopful of cells and incubated overnight at 30°C in a rotary shaker (180 rpm). MSB broth (50 ml) with phenylalanine was inoculated from the LB broth culture with a starting optical density at 600 nm of 0.05 and incubated at 30°C in a rotary shaker (180 rpm). The strains were grown in MSB-phenylalanine twice, and when the optical density (600 nm) of the cells reached 2.0 in the second culture, triplicate MSB broth cultures containing either 3 mM DBF or 3 mM DXN were inoculated from each strain and optical density (600 nm) readings taken at specific times. All growth curves were plotted using Prism software (GraphPad, San Diego, CA).