Inducible Synthesis of β-Galactosidase in Disrupted Spheroplast of Escherichia coli

A membrane preparation obtained from osmotic lysate of spheroplasts of Escherichia coli cells showed an activity of synthesizing beta-galactosidase which was dependent upon oxidative phosphorylation. The synthesis was inhibited by the addition of actinomycin D or of chloramphenicol. The beta-galactosidase synthesized in the membrane preparation was completely released into the medium, while that synthesized in the spheroplasts and intact cells remained within the cells. The minimum concentration of the inducer, methyl-beta-d-thiogalactoside, required for the induction of beta-galactosidase was 5 x 10(-5)m for intact cells, 3 x 10(-4)m for spheroplasts and 1 x 10(-3)m for membrane preparation. Incorporation of labeled glucose into insoluble components in membrane preparation was extremely low compared with that in intact cells or in spheroplasts. Based on these and other observations, the nature of this membrane preparation is discussed in relation to the structure of E. coli cells.