FIG 7.

Regulatory functions of LfsT in SPD (spermidine) transport and T3SS activity. (A) Schematic of the SPD transport system comprised of the PotA–PotD proteins in P. aeruginosa. OM, outer membrane; PM, plasma membrane; IM inner membrane. (B) SPD transport activity analysis of the indicated strains. (C) Corresponding ATPase activity assays of the related strains. (D) RT-qPCR assay of the potA gene (encoding a polyamine transport protein) in the indicated strains. Details are described above. (E) Galleria mellonella-killing assay using the indicated strains for 24 h. The group treated with phosphate-buffered saline (PBS) is the control group. (F) Detection of secreted ExoS (exoenzyme S) in different bacterial supernatants by Western blotting. (G) RT-qPCR assay for popN (encoding a type III secretion outer membrane protein). (H) LacZ activity of the indicated DEG promoter-lacZ fusions in P8D carrying pUCP18 or pCTX. The experiments were independently replicated three times, and each sample was tested in triplicate (D to H) or sextuplicate (B and C). Data were analyzed by one-way ANOVA with Tukey’s multiple-comparison test (α < 0.05) to compare the mean differences between the related groups. ***, P < 0.001. Error bars show standard deviations.