Autolytic Release and Osmotic Properties of 'Protoplasts' from Staphylococcus aureus

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Abstract
SUMMARY: The cell wall of exponential phase Staphylococcus aureus (strain Duncan) loses its tensile strength in c. 2 hr. when the organisms are incubated at 25° in 1·2 m-sucrose at pH 5·8 and ionic strengtin 0·3. The ‘protoplasts’ thus released from the mechanical protection of the cell wall are stable in 1·2 m-sucrose but lyse in media of lower osmotic pressure. The mean internal osmotic pressure of the ‘protoplasts’ is c. 20 atmospheres; they are permeable to glycerol but not to sucrose or NaCl. The rate of ‘protoplast’ release varies with the rate of growth of the organisms at harvesting. After osmotic explosion of ‘protoplasts’ released from slowly growing organisms the plasma membranes may be recovered as spherical shells which disintegrate and condense into small particles on washing, and 75% of the weight of the cell walls may be recovered as hemispherical shells.