Fig. 1

Schematic of inserting the fused promoter–reporter element into P. aeruginosa. a A roughly 2.2 kb intergenic region between ORFs of PA3835 and PA3836 was PCR amplified and cloned into vector pDONR/Zeo obtained from Invitrogen-Thermo Fisher Scientific (Grand Island, NY). b Two unique sites, BglII (B) and Spe I (S) were sequentially created by site-directed mutagenesis with the BglII site located in the middle of the intergenic region, and the SpeI site located at 10 bp upstream of the BglII site. c The gentamicin resistance gene (Gm ^R) was amplified by PCR and inserted at the BglII site. d The long half-life version of gfp was inserted at the SpeI site, generating plasmid pDONR-NT0. e Promoter of PA3841was inserted upstream of gfp in pDONR-NT0, creating construct pDONR-NT3841P. The final plasmid was digested with XhoI, dephosphorylated, column purified and used to electroporate wild-type P. aeruginosa PAO1 according to a published method [6]. The promoter–reporter element was inserted into the chromosome by a double cross-over recombination event. Primers used were listed in Additional file 1: Table S1