Flow cytometry analysis of the green fluorescent protein accumulation in the strains under study. (A) Schematic representation of plasmid pS234G, carrying gfp under the transcriptional control of the IPTG-inducible P
promoter. The activity of P
is controlled by the transcriptional regulator LacIQ. The transcriptional terminators included in the plasmid backbone are depicted as T0 and T1. The elements in this outline are not drawn to scale. P. putida KT2440 (B), EM329 (C), and EM383 (D) carrying pS234G were grown on M12 minimal medium containing glucose and harvested in mid-exponential phase. Gray and green peaks represent non-induced and induced cells, respectively. The vertical dashed line indicates the background fluorescence of the corresponding strain carrying the empty pSEVA234 plasmid, used as a negative control. The results shown are from a representative experiment, and the fold change in fluorescence upon induction is indicated in each case. A.F.U., arbitrary fluorescence units.