Membrane alteration and the formation of metachromatic granules in Escherichia coli treated with p-fluorophenylalanine.

The effect of p-fluorophenylalanine (FPA) on growing cultures of Escherichia coli was studied with regard to the composition and morphology of the cell envelope. A cell wall fraction was prepared by autolysis in hypertonic medium, and the resulting spheroplasts were osmotically lysed to obtain a cytoplasmic membrane fraction. Incorporation of labeled phenylalanine, FPA, and N-acetylglucosamine into both fractions of FPA-inhibited cells suggested that the composition of the membrane changed with time, whereas that of the cell wall remained relatively constant. Amino acid analysis revealed changes in the composition of the membrane fraction after FPA inhibition. Electron micrographs of shadowed cells and membranes revealed the presence of electron-dense metachromatic granules during the early stages of FPA inhibition.