Kinetics of the Interaction of Colistin with Live Escherichia coli Cells by the Bioluminescence Method

Abstract

We obtain the kinetic dependences of the concentration of adenosine-5'-triphosphate (ATP) inside (ATP_in) and outside (ATP_ex) E. coli cells on the colistin concentration and incubation in a nutrient LB medium and saline using the optimized bioluminescence method. With an increase in the concentration of colistin and the duration of incubation of cells in a nutrient medium, the ATP_in value rapidly decreases to zero. In this case, the ATP_ex value increases, reaching the limit (20–30% of the initial ATP_in value), and does not change even after the complete cell death. The significant decrease in ATP_in can be explained by the decrease in the activity of the enzymes of the respiratory chain and ATP synthase, functioning in the inner membrane of the cell, damage to which during incubation with colistin leads to a decrease in the rate and even to a cessation of ATP synthesis. A comparison of ATP_in and ATP_ex during the incubation of cells in a nutrient medium and saline in the presence of colistin show that colistin has a more substantial bactericidal effect on growing, metabolically active cells. In contrast, nongrowing cells deprived of nutrition are more resistant to antibiotic action.