FIG 6.

Critical role of rpoS in the enhanced transformation ability of Δcrp and ΔcyaA mutants. (A) The transformation frequencies of double-knockout Δcrp ΔrpoS and ΔcyaA ΔrpoS mutants were compared with those of wild-type BW25113 and single-knockout ΔrpoS, Δcrp, and ΔcyaA mutants. (B) Results of a complementary experiment using Δcrp ΔrpoS and ΔcyaA ΔrpoS mutants with plasmid pRPS. Δcrp, ΔcyaA, Δcrp ΔrpoS, and ΔcyaA ΔrpoS mutants harboring empty plasmid pSU19 served as controls. (C) Effects on transformation frequency of inducing rpoS in Δcrp ΔrpoS (left) and ΔcyaA ΔrpoS (right) mutants at different time points. rpoS was induced without arabinose (−) or with 0.2% arabinose (+) added periodically after incubation. Δcrp, ΔcyaA, Δcrp ΔrpoS, and ΔcyaA ΔrpoS mutants harboring plasmid pARA served as controls. Significant values compared with the value for the Δcrp ΔrpoS/pARArpoS mutant or the ΔcyaA ΔrpoS/pARArpoS mutant without arabinose were determined by Student's test and are indicated with an asterisk (P < 0.05). Error bars signify standard deviations for the results of at least two independent experiments.