Fig. 1

The hypothetic schematics of regulatory networks of glycerol and lactate metabolism in P. putida KT2440, and the construction of P. putida KT2440 (ΔlldR). a The derepression of the glp genes expression is occurring when the strain cultured in MSM with glycerol as carbon source. On the other hand, the expressions of lldPDE genes are repressed by the LldR, without the lactate as inducer. b The derepression of the lldPDE genes expression is occurring when the strain cultured in MSM with dl-lactate as carbon source. On the contrary, the free tetrameric assembly of GlpR will tightly bind to the DNA operator sequence with the DNA-binding domains, and inhibit the expressions of glp genes. c If the lldR gene is deleted, the repression of the lldPDE genes expression will be damaged, owing to the absence of the functional LldR. And the lldPDE genes will still fully express, even without lactate as the inducer. d Diagram illustrating the disruption of the lldR mediated by homologous double crossover. e Analysis of PCR fragments to confirm lldR disruption. Lane M molecular mass standard (λDNA/HindIII); lane 1 product amplified with P. putida KT2440 genomic DNA as the template; lane 2 product amplified with water as the template (negative control); lane 3 product amplified with P. putida KT2440 (ΔlldR) genomic DNA as the template. The PCRs were performed with primers lldRk.f and lldRk.r