Some features of the bacterial membrane studied with the aid of a new fractionation technique.

Membranes of Bacillus megaterium and other bacteria were bound to crystals of cadmium lauroylsarcosinate and were resolved into nine lipoprotein fractions by elution with potassium chloride and sodium deoxycholate solutions. The fractions differed widely in protein/lipid ratio. Some major protein species were probably common to all the fractions, but the phospholipid composition showed some variation. Electron-microscopic examination after negative staining revealed that material in certain fractions was in the form of particles of diameter about 12nm, and other fractions consisted of amorphous aggregates. The composition of the membrane in terms of the nine fractions was influenced markedly by the conditions of culture of the bacteria. Radioactive-labelling experiments suggested that some fractions served as precursors of others, and one fraction appeared to contain the attachment points of the DNA.