[Physiological activity of Escherichia coli cells studied by the spin exchange method]

The respiration and reducing activity of Escherichia coli M-17 cells was studied at physiological temperatures using the phenomenon of spin exchange between water-soluble nitroxyl radicals and molecular oxygen in liquid bacterial media. The peak intensity of the EPR signal from nitroxyl probes was characterized by a two-stage kinetics. The first stage was due to the rapid uptake of dissolved O2 whereas the second stage was caused by the anaerobic reduction of free radicals. The maximal rates of respiration and radical reduction were found at 45 to 55 degrees C. The rate of cell respiration changed when lipids underwent a gel-liquid crystal structural transition.