Figure 6
Visualization of nitrate-inducible luciferase activity. Parental wild-type spheroids and transformants expressing the g-luc reporter gene under control of the nitA promoter (NitLuc-A172 and NitLuc-X221) were investigated for light emission as a result of luciferase activity both under standard conditions (standard) and after induction by a switch from NH4 + to NO3 − (induced). Upper row: standard photo showing the assay setup. Middle row: photo (30 s exposure) without any extraneous light after addition of the coelenterazine substrate. Lower row: exposure to a light-sensitive film for 10 min after addition of the coelenterazine substrate.