Figure 1

Evaluation of oxygen-sensing cells using pNar-GFPuv construct. Lee and coworkers demonstrated the E. coli nar promoter is maximally induced at microaerobic oxygen levels (1–2% of air saturation, left panel). Identical fermentors were run in parallel and in triplicate, with identical inoculums and operating conditions but with one exception: one tank was equipped with one impeller, the other with four. Our motivation was to test whether the cells would differentially express GFP as they grew and circulated around the tanks.