FIG 1 .
RyhB represses expression of erpA. (A) A plasmid library allowing the expression of 26 sRNAs, as well as the empty vector, was transformed in the strain containing the PBAD-erpA-lacZ fusion. The effect of the overexpression of each sRNA expressed individually was measured by growing the cells for 6 h in LB containing 100 µg/ml ampicillin, 0.02% arabinose, and 100 µM IPTG, after which β-galactosidase activity was measured. Results are represented as a function of the fold change in activity of the fusion for each overexpressing plasmid compared to the plac empty vector. Dashed lines represent the threshold that was chosen to consider significant effects. Error bars represent standard deviations for a total of 8 independent experiments. (B) (Left) The PBAD-erpA-lacZ-containing strain was transformed with the empty plac vector or with the pRyhB plasmid containing ryhB under the control of an IPTG-inducible promoter. Strains were grown in flasks containing LB with 100 µg/ml ampicillin, 0.02% arabinose, and 100 µM IPTG for 6 h, after which β-galactosidase activity was measured. (Right) The strain containing the PBAD-erpA-lacZ fusion and a ryhB isogenic mutant were cultivated in LB with or without 250 µM DIP for 6 h before β-galactosidase activity was measured. Arbitrary units were empirically determined to be approximately equivalent to Miller units. Each point represents the mean from 8 or more experiments; error bars represent the standard deviations.