Effects of Phosphatidylinositol on Bacterial Protoplasts

Effects of phospholipids on the bacterial protoplasts or membranes were investigated. Phosphatidylinositol (PI) has, most of all, active bursting action on the protoplasts of Bacillus megaterium which was found to contain a very small amount of inositol, about 0.006% of dry cell weight. This action of PI was less active on the spheroplasts or protoplasts of Escherichia coli or Bacillus subtilis than Bac. megaterium. The bursting action of PI was dependent on temperature, but not on pH or osmotic pressure(concentration of sucrose). This action of PI on the protoplasts of Bac. megaterium was more marked when the incubation was carried out in phosphate buffer than in Tris buffer. High concentration of Mg ion inhibited this PI action in the phosphate buffer, but accerelated that in the Tris buffer.

Phospholipids, especially PI, elevated the activity of succinate dehydrogenase of membrane fraction of Bac. megaterium, but sodium laurylsulfate (SLS) inhibited this enzyme.

These actions of PI were compared with those of other phospholipids and detergenic Substances.