Biochemistry of the K antigens of Escherichia coli. Formation of the nucleoside diphosphate sugar precursors of the K27 antigen of E. coli 08:K27(A):H-

Tris(hydroxymethyl)aminomethane buffer modification of Escherichia coli outer membrane permeability

The effect of tris(hydroxymethyl)aminomethane (Tris) buffer on outer membrane permeability was examined in a smooth strain (D280) and in a heptose-deficient lipopolysaccharide strain (F515) of Escherichia coli O8. Tris buffer (pH 8.00) was found to increase outer membrane permeability on the basis of an increased Vo of whole-cell alkaline phosphatase activity and on the basis of sensitivity to lysozyme and altered localization pattern of alkaline phosphatase. The Tris buffer-mediated increase in outer membrane permeability was found to be dependent upon the extent of exposure to and concentration of the Tris buffer. The Tris buffer effects were demonstrated not to be due to allosteric activation of cell-associated alkaline phosphatase and were specific for Tris buffer. Exposure of cells to Tris resulted in the release of a limited amount of cell envelope component. Investigators utilizing Tris buffer are cautioned that Tris is not physiologically inert and that it may interact with the system under investigation.

Determinants that increase the serum resistance of Escherichia coli

The rfb locus, determining biosynthesis of O8-specific lipopolysaccharide side chains, was transferred to a rough mutant of Escherichia coli; recombinants producing a complete lipopolysaccharide were more resistant to the complement-mediated bactericidal action of human serum than the rough recipient. Inheritance of the his-linked genes for K27 antigen production did not alter the response to serum. The serum resistance of strains carrying O8 side chains, but not of strains with incomplete lipopolysaccharides, was further increased by inheritance of plasmids R1 and NR1.20

Demonstration by membrane reconstitution of a butanol-soluble intermediate in the biosynthesis of the O9 antigen of Escherichia coli

The activity in vitro of the mannan-synthesizing system of Escherichia coli O9 depends on the presence of glucose in the growth medium of the bacteria. Inactive membranes of E. coli strain F988 grown without gain mannan-synthesizing activity by reconstitution with a butanol extract obtained from the same bacteria grown with glucose. Inactive membranes could also be restored to biosynthetic activity by incubation with UDP-glucose in the presence of magnesium chloride. In this magnesium-ion-dependent reaction, a glucolipid was formed which was extractable with butanol. It could be used for the reconstitution of inactive membranes. The products of incubations with GDP-mannose of reconstituted and active membranes were analysed for electrophoretic mobility in sodium dodecylsulfate/polyacrylamide gel electrophoresis, molecular weight and composition. In all cases they proved to be the mannan attached to a hydrophobic mannose carrier, presumably a glucolipid. These results suggest that a glucolipid is the intermediary mannose acceptor in the biosynthesis of the O9 antigen.