FIGURE 4.

Complementation by Hfq variants of rpoS expression. (A) RO91-Δhfq (light-gray) and RO91-Δhfq arcZ mutant (dark-gray) were transformed with pACYC184 derivative plasmid expressing either wild-type or C-terminally truncated Hfq proteins from E. coli and C. difficile giving pEc-Hfq, pEc-Hfq core, pCd-Hfq, and pCd-Hfq core, respectively. The empty vector was used as a control (p). β-galactosidase activity from the rpoS-lacZ chromosomal fusion was measured in exponentially growing cells at 37°C (OD₆₅₀ of 0.4). Each value is the mean of three independent experiments, with standard deviations not exceeding 15% of magnitude. (B) Northern blots showing ArcZ, ArcZ*, and DsrA in RO91-Δhfq transformed with the same plasmids (as in Fig. 3). (**) A 61 -nt long DsrA processed fragment identified in Repoila and Gottesman (2001). (C) Northern blots showing ArcZ, ArcZ*, and DsrA in IBPC 928 transformed with the same plasmids, grown at 30°C, and shifted for 15 min to 44°C to inactivate thermosensitive RNase E. Relative amounts of ArcZ and DsrA normalized to 5S RNA are indicated.