Fig 3.

TetR system. (A) Growth curves were performed in Chamberlain's defined medium (CDM) with LVS bearing plasmid pEDL40 in the presence of ATc at concentrations of 0, 100, and 250 ng ml⁻¹ and LVS bearing pEDL41 ΔtetR as the constitutive control. The absorbance at OD₆₀₀ and luminescence were monitored every 15 min for 36 h. To determine the relative light produced per bacterium, the luminescence was divided by the absorbance and is represented as RLU/OD₆₀₀. (B) A growth curve was performed in CDM with LVS bearing pEDL41. The absorbance at OD₆₀₀ and luminescence were monitored every 15 min for 36 h. The RLU and OD₆₀₀ were plotted on separate y axes. (C) Growth curves were performed in CDM utilizing ATc concentrations from 0 to 50 ng ml⁻¹ in 10-ng ml⁻¹ increments, and luminescence per bacterium was monitored as described above. (D) A mid-log culture of LVS/pEDL40 was induced with 250 ng ml⁻¹ ATc to test the induction time. Luminescence was monitored every 15 min to ascertain the time it took to increase above 50 RLU, which represents the limit of detection. (E) A gentamicin protection assay was performed with LVS bearing plasmid pEDL40, with LVS bearing pEDL41 ΔtetR as the constitutive control. Induction was at 23 h postinfection with ATc concentrations of 0, 100, and 250 ng ml⁻¹. Luminescence was measured every 15 min for 5 h after induction.