Fig. 5

The latter part of the ermB regulatory region is key for the induction of ermB expression by spiramycin and tylosin. A Codons 10(Asp) and 11(Lys) of WT ermBL were mutated to isoleucine and serine, respectively, to mimic the identified P- and A-site codons in ribosomes stalled at ermCL. B Codons 9 (isoleucine) and 10 (serine) of WT ermCL were mutated to aspartic acid and lysine, respectively, to mimic the identified P- and A-site codons in ribosomes stalled at ermBL. C The first part of the ERY-inducible ermCL-lacZα reporter plasmid is a substitute for ErmBL-controlled ribosome stalling (M1-K11), named BL-CL. D The first part of the ERY-inducible ermBL-lacZα reporter plasmid is a substitute for ErmCL-controlled ribosome stalling (M1-S10), named CL-BL. β-Galactosidase activity assay and disc diffusion assay of these mutants exposed to erythromycin, spiramycin and tylosin. Miller units of β-galactosidase activity are shown on the Y-axis. The number on the top of each bar represents the fold change in beta-gal activity between the antibiotic and DMSO group. The error bars correspond to the SEM of three independent experiments. All the β-Galactosidase activity of antibiotics group compared to DMSO group is significantly. P < 0.05; (unpaired two-tailed Student’s t test)