K ⁺ -Dependent Deplasmolysis of a Marine Pseudomonad Plasmolyzed in a Hypotonic Solution

Abstract

When cells of a marine pseudomonad were washed with a solution consisting of 0.3 M NaCl, 0.05 M MgSO4, and 0.01 M KCl (complete salts), they maintained their normal morphology. When washed with a solution of 0.05 M MgSO4, they became plasmolyzed as indicated by both phase and electron microscopy. Suspensions of cells washed with 0.05 M MgSO4 showed an increase in optical density (OD) when 0.3 M NaCl was added, and this was followed by a decrease in OD upon the further addition of 0.01 M KCl. Salts of other monovalent cations were not effective in replacing K+ in producing the OD decrease. Phase-contrast microscopy revealed that the increase in OD was accompanied by a decrease in cell size, and the decrease in OD, by an increase in the cell size. Both phase and electron microscopy showed that the K+-dependent decrease in OD was accompanied by deplasmolysis of the cells. Na+ was required in the suspending medium in addition to K+ to obtain deplasmolysis. The intracellular K+ concentration in cells which had been washed with complete salts and which had retained their normal morphology was found to be 0.290 M. In cells plasmolyzed by washing with 0.05 M MgSO4, the intracellular K+ concentration was 0.004 M. Deplasmolyzed cells contained 0.330 M K+. The membrane profile of plasmolyzed cells was retained when protoplasts were formed. The protoplasts became spherical if incubated in a solution permitting the deplasmolysis of the parent cells. The evidence obtained indicates that plasmolysis and deplasmolysis under the conditions described was due to the loss and gain, respectively, of K+ by the cells. The effect of Na+ could be ascribed to its capacity to control the porosity of the cytoplasmic membrane of this organism. 850

Potassium uptake and retention by Oceanomonas baumannii at low water activity in the presence of phenol

“…Cultures were grown overnight by shaking (200 rpm) at 25³C. After incubation, aliquots of cells (5 ml) were washed twice in magnesium sulfate (10 mM) to deplete the cells of K [19] and inoculated into 50 ml of potassium limited MSM. Cells were incubated for 200 h and then either 5 mM KCl, RbCl or CsCl was added, and optical density was monitored at 660 nm.…”

Characterization of Putrescine Production in Nongrowing Vibrio parahaemolyticus Cells in Response to External Osmolality

“…The K+ release occurred without a time lag in every case. Since Na+ has been reported to be predominantly present in Vibrio species at a concentration similar to that of K+ (18,19), it was conceivable that Na+ would be released with K+ (16,19). Thus, we considered that the enhancement of Put production might be attributable to the reduction in the cellular concentrations of Na+ and K+, which would lead to the increase in activities of the preexisting ADC and/or AUH.…”

Salt requirements for membrane transport and solute retention in some moderate halophiles

“…When A. haloplanktis was washed free of Na ÷ by suspension in, and centrifugation from, a 50 mM MgSO 4 solution the cells required the presence of both Na ÷ and K ÷ in the suspending medium for the transport of AIB [9]. Cells washed with the Mg 2÷ solution lost their K ÷ [10] and when suspended in a salt solution containing 0.3 M Na ÷ became loaded with Na ÷ [11]. On incubation in the presence of K ÷, Na + was extruded from the cells as K ÷ accumulated.…”