Changes in physiological parameters of Escherichia coli during antibiotic-induced stress response
Understanding the mechanisms of bacterial response to stress caused by antibiotics is necessary to find ways to optimize the use of existing antibiotics and create new antibacterial drugs. Using a complex of microbiological and biochemical methods in combination with real-time monitoring of dissolved oxygen
and sulfide by electrochemical sensors, we studied changes in the growth rate, respiration, membrane potential, glutathione (GSH) and sulfide under the action of bactericidal antibiotics with various intracellular targets. Ciprofloxacin (CF),
kanamycin (Kan), and cefotaxime (Cef), which inhibit DNA, protein, and cell wall synthesis, respectively, caused growth and respiration inhibition, a drop in membrane potential, glutathione release from cells, and death of a significant part
of the population. The maximum inhibition of growth, respiration and membrane potential was observed under the action of cefotaxime, which provoked cell lysis. However, the rate of CFU decline in cultures treated with cefotaxime was lower than with other antibiotics. Under action of ciprofloxacin and kanamycin, E. coli continued to accumulate GSH in the medium during the entire experiment, which indicated its ongoing synthesis. In case of cefotaxime, the release of GSH from cells ceased after 60 min of exposure to this antibiotic. The action of ciprofloxacin was accompanied by the generation of sulfide, which was recorded by the sulfide sensor as a sharp reversible drop in the electrode potential. Therefore, the effect
of antibiotics on growth, respiration, membrane potential and GSH synthesis was inversely related to their killing activity.
