Uptake of rubidium and phosphate ions by polysaccharide-producing bacteria.

Abstract

Numerous mechanisms for the phenomena of inorganic salt uptake by biological systems have been postulated, and theories to explain them have been proposed. These mechanisms and theories fall into two categories: (a) the postulation of the existence of regions on the cell membrane possessing special chemical properties, and (b) the interpretation of the phenomena on the basis of special electrical or physical characteristics possessed by the cell membrane. The work of Spiegelman and Reiner (1942) gave strong evidence against a selective mechanism based on electrostatic barriers. On the basis of energy requirements, these authors believed that chemical as distinguished from electrical forces provide an answer to potassium and sodium balance studies. Overstreet and Jacobson (1946) and Jacobson and Overstreet (1947) stated that possibly more than merely exchange of ions held by electrovalent linkage was involved in the initial uptake of ions by biological systems. On the basis of their experiments they postulated a chemical binding substance which is impermeable to free inorganic ions. With this assumption, it was necessary to postulate that the connecting link is permeable to complexes of the ion or to certain organic compounds. Several properties which the ion-binding compounds must possess to account for certain characteristic features of the absorption were outlined, and the lability of the complex within the cell was stressed. Most phytophysiologists now agree that ion accumulation must take place by means of a coupling with intracellular processes, the mechanics of which are largely a matter of conjecture. The view that both the role of metabolism and specificity in the absorption can best be accounted for by the assumption that metabolic