Streptomycin

Tetracycline, oxyTetracycline, chlorTetracycline, doxycycline, ethidium bromide (EB), Hoechst33342 stain, cefoperazone, cefazolin, streptomycin, ampicillin, roxithromycin, chloramphenicol, rifampicin, norfloxacin, deoxycholate, sodium cholate, ofloxacin, doxorubicin, daunorubicin, acridine flavin, and quinine were purchased from Coolaber (Beijing, China), and ortho-vanadate was purchased from Sigma-Aldrich (St. Louis, MO, United States). Carbonylcyanide m-chlorophenylhydrazone (CCCP) and reserpine were obtained from MedChemexpress (Monmouth Junction, NJ, United States). Drug-sensitive paper was purchased from Hangzhou Microbial Preparation (Hangzhou, China).

Tetracycline, oxyTetracycline, doxycycline, rifampicin, norfloxacin, cefminox, cefazolin, daunorubicin, doxorubicin, streptomycin, roxithromycin, deoxycholate, chloramphenicol, ofloxacin, acridine flavin, sodium cholate, ampicillin, quinine, Hoechst 33342, and ethidium bromide were from Coolaber (China). Ortho-vanadate was from Sigma-Aldrich (USA). Carbonylcyanide m-chlorophenylhydrazone (CCCP) and reserpine were from MedChemexpress (Monmouth Junction, USA). norfloxacin disks were from Hangzhou Microbial Preparation (China). Gel extraction kits were from ThermoScientific. Wizard SV Gel and PCR Clean-UP System were from Promega (Promega, USA). DH5α competent cells were from Tiangen Biochemical Technology Co., Ltd. (China). Competent cell preparation kits were from TaKaRa (Japan).

E. coli cells were subject to the shock of various abiotic stresses including hyperosmotic shock, acid shock, oxidative shock and treatment by ciprofloxacin or streptomycin. The exponential cultures (wild type strain, rpoS-null strain or their RelA∗ OE strains with 30 μM IPTG) were first growing to OD₆₀₀ $\approx$ 0.3 before subjecting to various abiotic stresses. For the hyperosmotic shock experiment, the shock medium was M9 glucose minimal medium contained an additional 2 M sodium chloride (NaCl). The exponential culture was quickly collected by a 0.22 μm filter membrane using a vacuum filtration system. The cells in the membrane were then transferred into the shock medium to initiate a time-course hyperosmotic shock experiment. At different time points after shock, serially diluted cultures were plated on solid LB agar for cell counting. For the acid shock experiment, the shock medium was EG medium (0.2% glucose, 57 mM K₂HPO₄, 17 mM NaNH₄HPO₄, 10 mM citrate, 0.8 mM MgSO₄, adjusted to pH 2.5 by HCl).⁶⁵ (link) The procedure was similar as described for hyperosmotic shock. For oxidative shock, 20 mM hydrogen peroxide (H₂O₂) was directly supplied into the medium. Similarly, 20 ng/mL ciprofloxacin (Sigma) or 100 μg/mL streptomycin (Coolaber, Beijing) was directly supplemented into the medium for antibiotic treatment.