Apr 6, 1976

The state of energization of the membrane of Escherichia coli as affected by physiological conditions and colicin K

G J Brewer


The bacterial protein colicin K, when added to sensitive Escherichia coli in the presence of 3,3'-dihexyloxacarbocyanine, cuases a doubling in fluorescence of the probe. Glucose and oxygen cause a decreased fluorescence while anoxia and cyanide cause a rise in fluorescence. These results in conjunction with the work of other laboratories suggest that colicin K causes a depolarization of the transmembrane electrical potential. Fluorescence in the absence of colicin K was relatively independent of KCl, NaCl, and MgCl2 concentrations below 0.1 M. Although colicin K caused rapid efflux of the K+ analogue 86Rb+, the fluorescence rise was only partially blocked by 0.13 M KCl. The level of fluorescence caused by the action of colcin K was inversely proportional to the logarithm of the concentration of MgCl2 over the range of 2 muM to 4 mM. This suggests that a Nernst electrochemical potential for an anion can counteract a membrane depolarization caused by colcin. After colcin K action, the fluorescence of the carbocyanine could be further increased by anoxia or cyanide. The distribution of the weak base dimethyloxazolidinedione indicated that the pH in the interior of aerobic E. coli supplied with lactate was alkaline by 0.1 unit and ...Continue Reading

Mentioned in this Paper

Bacterial Proteins
Alkalescens-Dispar Group
Resting Potentials
Electron Transport
Glucose, (beta-D)-Isomer
Integral to Membrane
Fluorescence Spectroscopy

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