FIGURE 1.

YchF is involved in regulating multiple stress responses in E. coli. (A) E. coli wild-type cells or the ΔychF strain were inoculated in LB medium and grown to OD₆₀₀ of ∼0.5 before serial dilution in LB medium. Of each dilution, 10 μl cell suspensions were spotted onto LB plates containing 2 mM H₂O₂ or 150 μg/ml fusidic acid when indicated. Cell growth was analyzed after overnight incubation at 37°C. (B) As in A, but cells were incubated on plates containing 7 mM hydroxyurea (HU) and 0.002% arabinose under aerobic and anaerobic conditions. ΔychF + pBadYchF refers to the deletion strain carrying a plasmid-encoded ychF copy under the control of the arabinose promoter. (C) The indicated strains were grown on LB medium or LB medium with 7 mM mM HU and analyzed microscopically. ImageJ was used to determine the cell length of at least 400 individual cells. Values are shown as a box plot, in which the box reflects 75% of all measured values and the line inside of the box the mean value. The dots reflect values outside of the 95% confidence interval. The p-value was determined by a double t-test and (****) corresponds to p < 0.0001. n.s. not significant. (D) Equal numbers of wild-type and ΔychF(Km^R) cells were inoculated in LB medium as co-culture and at the indicated time points the number of colony forming units (CFU) on LB and LB-Km plates were determined. The mean values of n ≥ 3 experiments are shown and the error bars represent the standard error of the means (SEM). (E) 10⁸ cells of the indicated strains grown on LB medium in the presence of 0.002% arabinose were precipitated with 10% trichloroacetic acid (TCA) and the pellet was separated by SDS-PAGE, and after western transfer analyzed with antibodies against Pth and YchF. Representative images/gel blots of at least three independent experiments are displayed.