Bacterial proteins.—The presence of alcohol-soluble proteins

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Abstract
In the course of an investigation of the Gram-staining material in Strepto­cocci and Staphylococci, substances giving the general reactions of the alcohol-soluble proteins or gliadins have been isolated. Alcohol-soluble proteins, or prolamins (Osborne (1)), are especially characteristic of the seeds of cereals; among them gliadin of wheat and rye, hordein of barley, and zein of maize are typical examples. The present communication deals with the alcohol-soluble fraction of bacterial protein: the other soluble protein substances will form the subject of a later communication. The work was commenced in 1917 as part of the author’s study of war wounds, but had to be abandoned, and was not recommenced until the winter of 1923. Most investigations on bacterial proteins have been conducted by extracting the bacterial cells with alkaline solutions, with or without heating; such a pro­cedure is likely to modify certain of the proteins, and, as will be seen later, would entirely remove the alcohol-soluble fraction. Bacteria are especially resistant to the solvent action of the majority of biochemical solvents used for the extraction of proteins. The Gram-positive organisms, with the exception of Pneumococci, which are soluble in bile (Heidelberger and Avery (2) used this method in examining the protein of Pneumo­cocci) are especially refractory. Douglas and Fleming (3) extracted Staphylo­cocci with hot acetone and removed the Gram-reacting substance; Dreyer (4) used acetone and boiling formalin. All these processes are likely to alter the residual proteins. Liquid cultures are also unsatisfactory, are bulky to manipulate, and introduce disturbing factors.

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