[Characteristics of the sulfate requirement of propionic acid bacteria]

The kinetics of sulfate assimilation by Propionibacterium shermanii was found to be peculiar. The assimilation and excretion of sulfate into the medium had an oscillatory character. Sulfate was shown to pass into the cell by active transport. Sulfate transport is described by the Michaelis--Menten kinetics. Thiosulfate and sulfite inhibit sulfate assimilation. Cysteine does not entirely inhibit sulfate assimilation by the cells. The system of sulfate transport was repressed by cysteine to a small extent. The intracellular pool of inorganic sulfate changed in the process of culture growth.