Osmolarity of periplasm

Value 300 mOsm
Organism Bacteria Escherichia coli
Reference Stock JB, Rauch B, Roseman S. Periplasmic space in Salmonella typhimurium and Escherichia coli. J Biol Chem. 1977 Nov 10 252(21):7850-61 p.7860 right column 2nd paragraphPubMed ID334768
Method The cytoplasmic, periplasmic, and total cell volumes were all derived from the distributions of solutes in cell suspensions, The rationale is illustrated in Fig. 1. Inulin, because it is large, cannot penetrate the outer membrane and is located only in the extracellular fluid. Sucrose, without the aid of a permease, cannot cross the plasma membrane and is located only in the periplasm and extracellular fluid. Water moves freely throughout the cell it is located in the cytoplasm, periplasm, and extracellular fluid. From Table V, the osmotic strength can be calculated as 270 mosM in Medium 63. The reciprocal of the graph in fig. 6 is Xcyto=0.36 mosmol/g dry weight of cells. The cells used in these experiments were grown in medium 63 in this case Vcell was 1.6 and Vcyto was 1.2 ml/g dry weight of cells. The intracellular osmotic strength was, therefore, 300 mosM (Xcyto/Vcyto) in agreement with the values obtained by the other methods.
Comments A Donnan equilibrium between the periplasm and the extracellular fluid, and that the periplasm and cytoplasm are isoosmotic. In minimal salts medium, the osmotic strength of the cell interior was estimated to be approximately 300 mosM, with a net pressure of approximately 3.5 atm being applied to the cell wall.
Entered by Uri M
ID 104054