Sites of the Incorporation of an Amino-acid into Proteins of Bacillus megaterium

Abstract

WHEN the digestion of B. megaterium is carried out with lysozyme in suitable media of high osmotic pressure, the rod-shaped cells are converted into from one to four spherical protoplasts¹. It has been shown by McQuillen that these protoplasts are capable of growing and dividing, and of effecting the synthesis of protein, nucleic acids, and adaptive enzymes². If the medium in which the protoplasts are suspended is diluted, the cytoplasmic membranes surrounding the protoplasts burst and much of the cytoplasmic constituents is liberated into the medium¹. This liberated cytoplasm contains no particles equivalent to the mammalian microsomes, ultracentrifugal analysis having shown that not more than 10 per cent of the material has a maximum molecular weight of 200,000, the residue being of much lower molecular weight. The bulk of the deoxyribonucleic acid of the cell remains associated with the ‘ghost’ cytoplasmic membranes and may be sedimented with them at low speeds on a bench centrifuge.