Studies of antibiotic resistance pumps teta and acrab activity in escherichia coli cells

We used lipophilic tetraphenilphosphonium (TPP+) ions for functional analysis of multidrug resistance (MDR) pumps TetA and AcrAB in Escherichia coli cells. We have found that tetracycline increases the cell outer membrane permeability to lipophilic compounds. Tetracycline entered the cells faster when the bacterial outer membrane was permeabilized using EDTA. These results indicate that tetracycline enters the cell not only through the porins, but also it penetrates the lipid bilayer of the outer membrane. MDR pumps extruding TPP+ ions from E. coli cells, also interact with tetracycline and chloramphenicol. Genes of TetA pump are induced, when the cells are incubated with low concentrations of tetracycline. On the other hand, incubation of the cells with tetracycline disturbs the activity of others MDR pumps in E. coli. Reserpine and chlorpromazine effectively inhibit activity of tetracycline-extruding MDR pumps, but Phe-Arg-β-naphtylamide does not show any inhibitory activity. Finally, it has been shown that action of the MDR pump inhibitors is stronger, when they are added to the bacterial suspension in the absence of antibiotics