OSMOTICALLY INDUCED CHANGES OF CELL SPACES IN NEISSERIA MENINGITIDIS COMPETENCE VARIANTS

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Abstract
The volume of the whole cell and the fraction of the intact cell bounded by the cytoplasmic membrane (protoplast volume) were measured by dextran and 14C-sucrose exclusion spaces in N. meningitidis competence variants. Increase in external osmotic pressure causes contraction of the protoplast volume. Increasing osmolality due to NaCl and MgCl2 also causes contraction of the volume of the whole cell, whereas increasing concentrations of sucrose cause little or no change in the whole cell volume. A significant difference between competent (cp+) and incompetent (cp-) cells was shown. The cp+ protoplast have a far higher capacity for swelling during decreasing osmolality and for shrinkage during increasing osmolality. Comparison of spheroplasts obtained by autolysis and by the penicillin technique indicates that the average cp+ spheroplast is larger than the average cp- one. The significance of the difference in structure of cp+ and cp- protoplasts was discussed.