AgNO₃ dependant modulation of glucose mediated respiration kinetics in Escherichia coli at different pH and...

The inhibitory role of AgNO₃ on glucose-mediated respiration in Escherichia coli has been investigated as a function of pH and temperature using Clark-type electrode, environmental scanning electron microscopy, and computational tools. In the given concentration of bacterial suspension (1 × 10⁸  CFU/ml), E. coli showed an increasing nonlinear trend of tetra-phasic respiration between 1-133 μM glucose concentration within 20 min. The glucose concentrations above 133 μM did not result any linear increment in respiration but rather showed a partial inhibition at higher glucose concentrations (266-1066 μM). In the presence of glucose, AgNO₃ caused a concentration-dependent (47-1960 μM) inhibition of the respiration rate within 4 min of its addition. The respiration rate was the highest at pH 7-8 and then was decreased on either side of this pH range. The inhibitory action of AgNO₃ upon bacterial respiration was the highest at 37 °C. The observations of the respiration data were well supported by the altered bacterial morphology as observed in electron microscopic study. Docking study indicated the AgNO₃ binding to different amino acids of all respiratory complex enzymes in E. coli and thereby explaining its interference with the respiratory chain. Copyright © 2016 John Wiley & Sons, Ltd.