FIG 6.

Susceptibility of planktonic cells differing in c-di-GMP levels due to overexpression of genes encoding phosphodiesterases and diguanylate cyclases to colistin and tobramycin. (A) Susceptibility of planktonic cells overexpressing dipA, rbdA, and PA2133 encoding phosphodiesterases, to colistin. (B) Susceptibility of planktonic cells overexpressing nicD and PA3343 encoding diguanylate cyclases to colistin. (C) Susceptibility of planktonic cells overexpressing dipA, rbdA, and PA2133 encoding phosphodiesterases to tobramycin. Strains were grown to the exponential and stationary phases prior to treatment with colistin (20 μg/ml) and tobramycin (50 μg/ml) for 1 h at 37°C. Susceptibility is expressed as log₁₀ reduction in CFU. All experiments were carried out at least in triplicate. Error bars denote standard deviations. *, Significantly different from PAO1/pMJT1 grown to exponential phase; **, significantly different from PAO1/pMJT1 grown to stationary phase (P < 0.01 as determined by ANOVA and SigmaStat).