FIGURE 5.

Recombinant TatA production induces the phage shock response. A, SDS-PAGE/immunoblot detection of TatA (upper panel) and PspA (lower panel) in E. coli strains BW25113, BW25113 ΔpspA, MC4100, and MC4100 producing TatA-strep (migrating below the natural TatA band; anti TatA antibody detects both bands). Note that the PspA level is strongly induced by recombinant TatA-strep. B, induction of the phage shock response by recombinant TatA levels depends on the phage shock proteins PspB, PspC, and PspF. Detection of TatA-strep (upper panel) and PspA in the psp-wt strain BW25113 and its mutants deficient in pspA, pspB, pspC, or pspF, as indicated with or without recombinant TatA production. To gain a more complete view of PspA levels, PspA was detected in membrane fractions (m-PspA; middle panel) and in soluble fractions (s-PspA; lower panel); *, exclusively the Strep-tag and thus recombinant TatA is detected on this blot. C, LacZ activities of the pspA-promoter reporter strain MC3, 1 h after induction of pBW-tatA-strep. Cultures of strains containing the empty vector were used as negative controls (x). Note that the activation of the pspA promoter by TatA-strep production depends on the presence of PspB and PspC.