Transport of B-Vitamins in Microorganisms. II. Factors Affecting the Uptake of Labelled Thiamine by Nonproliferating Cells of Lactobacillus fermenti.

Abstract

The results of studies on the conditions affecting the uptake of labelled thiamine by non-proliferating cells of L. fermenti are presented. The uptake process was found to exhibit several features of enzyme mediated reactions it showed pronounced temperature and pH maxima, saturation kinetics and stereospecificity. It is demonstrated that the uptake reaction requires an exogenous source of energy and that the accumulation process is reversible. Both the uptake and the exit reactions are stimulated by potassium ions. The uptake process in stimulated by ascorbic acid and by magnesium ions. The existence of a stoichiometric relationship between the influence of energy and the influence of magnesium is demonstrated. Both the uptake and the exit processes are inhibited by phosphate, the latter to a much greater extent than the former. The uptake is inhibited by sodium pyruvate and by high levels of glucose. The ability of the non-proliferating cells to take up thiamine exhibits an inverse relationship to the thiamine content of the growth medium.