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

Abstract

The Neisseria meningitidis Strain M1 could grow in media made hypertonic with 0.7 M sucrose, but the growth rate was much reduced. The reduction was more pronounced in the competent (cp+) variant than in the incompetent (cp-) one. After exposure to increased osmotic pressure, growth was resumed after a pronounced lag which was regularly longer in the cp- variant. Cellular lysis took place during the lag. The lag could be shortened by the addition of MgCl2. N. meningitidis cells lysed slowly when suspended in various isotonic solutes, but rapid lysis was activated in exponential phase cells by exposure to hypotonic as well as to hypertonic conditions. This activation was more pronounced in the cp- variant than in the cp+ variant. In stationary phase cells there was very little activation of autolysis. The rate of autolysis was inhibited by MgCl2 and CaCl2 in low concentration. Osmotic fragility developed during autolysis in the presence of high concentrations of acetate or sucrose but not in the presence of high concentrations of NaCl or phosphate. MgCl2 increased the osmotic stabilization caused by acetate or sucrose, whereas CaCl2 in low concentration abolished the stabilizing effect of these solutes.