INFLUENCE OF OSMOTIC PRESSURE ON TRANSFORMABLE AND NON TRANSFORMABLE VARIANTS OF NEISSERIA MENINGITIDIS.

The reactions of competent ( cp +) and incompetent ( cp ‐ ) variants of the Neisseria meningi tidis Strain M1 to variations in the osmotic pressure have been compared by observing survival and absorbancy changes. Pronounced differences were observed. Both competence variants were very sensitive to osmotic pressures outside a range between approximately 4 and 7 atmospheres, but the cp + cells had a much higher survival when exposed both to increased tonicity and to hypotonic conditions. With the assumptions valid for similar systems, the undamaged N. meningitidis cells from both competence variants behaved as osmometers at least between osmotic pressures from around 1.5 atmospheres to above 24 atmospheres. Exposure of the cells to distilled water as well as to high osmolality, however, interfered strongly with the capacity of the cells to maintain an osmotic barrier, suggesting membrane damage. This impairment was far more pronounced in cp ‐ cells than in cp + ones, indicating that the cytoplasmic membrane of the cp + cell is relatively protected against deleterious effects of osmotic stress. Some implications of these findings have been discussed.