FIG. 3.

Expression of the plasmid R1-encoded T4S system elicits a cytoplasmic stress response. E. coli MG1655 cells without plasmid or harboring the repressed plasmid R1 or the derepressed plasmid R1-16 were analyzed by Northern blotting. groESL (A), dnaJK (B), and hslVU (C) transcript levels are increased in cells expressing the R1-16-encoded T4S genes. 23S rRNA is shown as a loading control. Numbers above the blots indicate minutes after dilution. Numbers at the bottom of the Northern blot shown in panel B indicate the relative signal intensity compared to the signal intensity in stationary phase. S, stationary phase.