FIG 1.

Hcp1 was upregulated in the ΔnrtR mutant. (A) The relative hcp1 mRNA levels in PAK, ΔnrtR, and ΔnrtR/att7::nrtR. Total RNA was isolated from bacteria at an OD₆₀₀ of 1.0, and hcp1 mRNA levels were examined by real-time qPCR using rpsL as an internal control. **, P < 0.01, by Student's t test. (B) Bacteria containing an hcp1-Flag driven by its native promoter were grown to an OD₆₀₀ of 1.0 in LB medium. Proteins from an equivalent number of P. aeruginosa cells of the indicated strains were separated on 12% SDS-PAGE and probed with an antibody against Flag or RpoA. (C) Competition assay between P. aeruginosa and E. coli. The indicated P. aeruginosa strains and E. coli were mixed at a 5:1 ratio, coincubated for 24 h at 25°C, resuspended in LB, and plated on LB agar plates with tetracycline. The E. coli recovery index represents the bacterial number of recovered DH5α/pDN19 with the number of DH5α/pDN19 in competition with PAK as 1.0. Bars represent the means from three experiments, and error bars indicate the standard deviation. ****, P < 0.0001, by Student's t test.