Factors Which Modify the Effect of Sodium and Potassium on Bacterial Cell Membranes

Abstract

Escherichia coli B, when placed in 0.2 to 0.5 M solutions of NaCl, KCl, or LiCl, show an increased turbidity. With NaCl, this increased turbidity is stable with time; with KCl and LiCl, it is gradually lost. The stability to NaCl with time is due to substances removable from the cell by incubation in phosphate buffer; these materials exist in water washings from such phosphate-incubated cells.

Salt-induced Contraction of Bacterial Cell Walls

“…For example, Johnson and Harvey (13) concluded from measurements of packed cell volume and light scattering that gram-negative Achromobacter (Photobacterium) fischeri cells shrank as much as 27% in volume when transferred from seawater to 2.5 times concentrated seawater. Salt-induced contraction of many other gram-negative bacteria has been reported (3,4,12,15), and there appeared to be a close association between whole cell shrinkage and observable plasmolysis.Gram-positive bacteria also can be made to shrink in salt solutions, even though they are not readily plasmolyzed. Dutky (unpublished data, cited in reference 14) found that Bacillus megaterium cells contracted from 15 to 25% when transferred from normal broth to broth containing 2 M NaCl.…”

Permeability of Bacteria to Inorganic Cations. A Comparison between a Psychrophilic Achromobacter Strain and Escherichia coli

“…Earlier reports agree on the permeability of potassium ions under these conditions (Bovell et aL 1963, Hennemau and Umbreit 1964, Knowles 1971. Under some circumstances sodium ions have also been found to penetrate the cells (Henneman and Umbreit 1964). The penetration of divalent ions has not heen examined as thoroughly.…”

“…Light-scattering technique has frequently been employed to examine the permeability of bacterial cells to small molecoles and ions (Bernheim 1963,, Bovel! et al 1963, Henneman and Umbreit 1964, Ljunger and Larsson 1973, Mitchell and Moyle 1956. This simple and rapid method reflects the behaviour of the living cell in response to variations of the ion concentration of the surrounding medium and involves little damage to the cells, when used at moderate salt concentrations.…”

Transport and Retention of K + and Other Metabolites in a Marine Pseudomonad and Their Relation to the Mechanism of Optical Effects

“…An optical density (OD) increase occurs in suspensions of many species of gram-negative bacteria when the solute concentration of the suspending medium is increased. This increase is often followed by a slow decrease to values approaching those prevailing initially (1,3,9,11,14). The first phase of this phenomenon, the increase in OD, has most often been ascribed either to plasmolysis of or to a decrease in the size of the cells caused by the osmotic action of a nonpenetrating or slowly penetrating solute.…”