Fig. 5From: Directed evolution of a transcription factor PbrR to improve lead selectivity and reduce zinc interference through dual selectionComparison of the trowth curves of the chassis cells with the selection plasmid in response to lead and zinc in the presence of sucrose. The optical density at 600 nm of the E. coli (pZE21-PBS) strain was measured with metal ions at a 20 µM and b 50 µM. Sucrose was used at 10 g L−1. Squares: lead ions; Circles: zinc ions. Experiments were performed in triplicate, and data represent the averages and standard deviations of the meansBack to article page