Kinetics of the reduction of tetrathionate by intact bacterial cells.

Abstract

The kinetics of the reduction of tetrathionate by washed nongrowing intact cells ofCitrobacter were studied. The rate of the reduction in most cases is not constant. The course of reduction usually resembles the first order kinetics within a limited, varying initial time period. This finding makes it possible to evaluate quantitatively the curves obtained experimentally of the relationship between concentration of the product and time, applyingequations valid for this reaction order, to determine the rate constant of the first order reaction and thus to determine the initial rate of the reduction of tetrathionate as the measure of the tetrathionate-reductaso activity of intact cells. Deviations from the first order kinetics, observed during later phases of the reduction are caused by excessive acidification of the medium. The effect of various experimental conditions on the initial rate of reduction of tetrathionate by the cells was also studied. The results presented served as a basis of a general method for the quantitative evaluation of the tetrathionate-reductase activity of intact bacterial cells.