Studies of the bacterial cell wall: IV. The composition of the cell walls of some gram-positive and gram-negative bacteria

Abstract

Some general properties of the cell walls of four Gram-positive and two Gram-negative bacteria have been studied. The rate of hydrolysis of cell walls of several bacteria, by 2 N HCl at 100° C, has been followed by estimation of liberated reducing substances and hexosamine. Several extraction procedures have been used in a study of the lipid content of the cell walls of E. coli and B. subtilis. Cell wall preparations have been analysed for their N and P contents, reducing substances and hexosamine liberated on acid hydrolysis and total lipid contents. The lipid content of the cell walls of the Gram-negative bacteria, E. coli and Salmonella pullorum is substantially higher than that of any of the Gram-positive cell wall preparations. The products of acid hydrolysis of cell walls have been examined by paper chromatography. The amino acids of the cell walls have been identified. The amino acids of Strep. pyogenes wall have been examined before and after removal of the type-specific M-protein with trypsin. Cell walls of some Gram-positive show very limited amino-acid constitutions, being devoid of aromatic and sulphur-containing amino acids. A much more complete range of amino acids including aromatic, certain sulphur-containing amino acids, arginine and proline, was found in the cell walls of the two Gram-negative species. The recently isolated amino acid, diaminopimelic acid, has been identified in the walls of certain bacteria. Three unknown ninhydrin-reacting substances have been appeared on chromatograms of cell wall hydrolysates. The sugar components of the cell walls have been identified. The presence of group specific substances in the cell wall of Strep. pyogenes has been demonstrated.