REDUCTION SITES OF TELLURITE AND TETRAZOLIUM SALTS IN LISTERIA MONOC YTOGENES

Abstract

Employing negative staining and thin sectioning techniques, the reduction sites of potassium tellurite and of tetrazolium salts in L. monocytogenes were revealed by electron microscopy. When the cells were negatively stained with phosphotungstate, the intracytoplasmic membrane system composed of complex lamellar and vesicular structures was distinctly demonstrated. Potassium tellurite was mainly reduced to metallic tellurium crystal on and/or near the inner layer of the cytoplasmic membrane but not in the intracytoplasmic membrane system.
Triphenyl tetrazolium chloride (TTC) was reduced to TTC-formazan on or in the intracytoplasmic membrane system. As the TTC-formazan was dissolved in ethanol during the dehydration, the site of the formazan deposit appeared as a transparent crystal-like area surrounded by parts of the membrane system in sections of the cells. These findings strongly suggest that the tellurite-reduction system may principally be located on or near the inner layer of the cytoplasmic membrane, whereas the dehydrogenase system of the tetrazolium salt may be associated mainly with the intracytoplasmic membrane system.