title: K plus-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 MgSO(4), and 0.01 m KCl (complete salts), they maintained their normal morphology. When washed with a solution of 0.05 m MgSO(4), they became plasmolyzed as indicated by both phase and electron microscopy. Suspensions of cells washed with 0.05 m MgSO(4) 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 MgSO(4), 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.
mesh_terms: D001693:Biological Transport, Active; D002462:Cell Membrane / Q000187:drug effects; D002463:Cell Membrane Permeability; D002473:Cell Wall; D003470:Culture Media; D005613:Freeze Etching; D007038:Hypotonic Solutions / Q000494:pharmacology*; D007477:Ions; D008274:Magnesium / Q000494:pharmacology; D008278:Magnesium Sulfate; D008854:Microscopy, Electron; D008858:Microscopy, Phase-Contrast; D009995:Osmosis; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology*; D011189:Potassium Chloride; D011523:Protoplasts; D011549:Pseudomonas / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology; D012965:Sodium Chloride; D013053:Spectrophotometry; D014871:Water Microbiology
chemical_list: D003470:Culture Media; D007038:Hypotonic Solutions; D007477:Ions; D012965:Sodium Chloride; D011189:Potassium Chloride; D008278:Magnesium Sulfate; D012964:Sodium; D008274:Magnesium; D011188:Potassium