RpoS-Dependent Mechanisms are Needed for Tetracycline Resistance but Are Not Involved in the Cross-Protection against Other Antibiotics in Escherichia coli

RpoS, an alternate sigma subunit of RNA polymerase, is upregulated under stress conditions such as high heat, depletion of nutrient, high osmolarity, and UV radiation. Current understanding is that RpoS acts as a general stress response regulator to counter the effect of different types of stress, including antibiotics, when it is induced by a single stress. In this study, we sought to test the cross-protection ability of RpoS production in E. coli to antibiotics streptomycin, chloramphenicol, and tetracycline. A pBADrpoS E. coli strain was created by using PCR to amplify the rpoS gene before cloning it into the pBAD TOPO vector. The ligated vector was chemically transformed into Wild type (WT) bacteria to create the new strain. To ensure that arabinose successfully induced rpoS, western blotting and immunodetection were used. WT E. coli BW25113, JW5437-1 ∆ rpoS, and pBADrpoS E. coli strains were then tested for antibiotic resistance. It was observed that the pBADrpoS strain showed decreased susceptibility to tetracycline only. An rpoS -dependent mechanism is involved in the increased resistance to tetracycline; however, there was no cross-protection observed against other antibiotics.