The translocator protein (TSPO), previously designated as peripheral-type benzodiazepine receptor, is an evolutionary conserved protein that is found in many Eukarya, Archae and Bacteria, in which it plays several important functions including membrane biogenesis, signaling and stress response. A tspo homologue gene has been identified in several members of the Pseudomonas genus, among which the soil bacterium P. fluorescens Pf0-1. In this bacterium, the tspo gene is located in the vicinity of a putative hybrid histidine kinase-encoding gene. Since tspo has been involved in water stress related response in plants, we explored the effects of hyperosmolarity and temperature on P. fluorescens Pf0-1 tspo expression using a strategy based on lux-reporter fusions. (B) Co-transcription of Pfl01_2810 and tspo by RT-PCR assay. RT-PCR was assayed on tspo (1), Pfl01_2810 (2) and on the putative operonic structure Pfl01_2810-tspo (3), using primers located into tspo (1) or Pfl01_2810 (2) ORFs, or into both tspo and Pfl01_2810 ORFs (3). RT-PCR achieved on total RNA did not lead to a PCR fragment (line 4, negative control). L: Ladder 1kb+ (Biorad ®), (C) Growth curves in microtitre wells in LB medium at 28 C and relative luminescence (RL) activity of pTSPO and pHK-TSPO in P. fluorescens Pf0-1. The tspo gene (Pfl01_2811) of P. fluorescens Pf0-1 forms an operonic structure with Pfl01_2810 and is expressed transiently during the bacterial growth. (A) Schematic representation of the genomic environment of tspo and of transcriptional fusions pTSPO and pHK-TSPO. Grey bars represent the beginning of the luxCDABE reporter cassette of the promoterless pAB133 vector. The position of the studied promoter region is indicated relatively to the translational initiation start of each ORF. Pfl01_ 2809 lux CDABE pHK-TSPO-253 bp lux CDABE pTSPO-227 bp P. fluorescens Pf0-1 chromosome lux transcriptional fusions Pfl01_2810 tspo