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Biomedical subjects

E C Heath

Publications and source records attributed to E C Heath.

At least 55 records · Page 3Linked to original sources
PubMed1973

Isolation and characterization of lipopolysaccharide protein from Escherichia coli.

Extraction of the cell envelope of E. coli with 1% sodium dodecyl sulfate yielded a lipopolysaccharide protein that was purified to homogeneity by conventional techniques. Analysis of the pure protein indicated that it is a complex lipopolysaccharide protein with the following molar ratios of constitutents: 3-deoxyoctulosonate, 1.0; glucosamine, 1.3; neutral sugar (glucose + heptose), 1.0; organic phosphate, 2.3; and amino acid, 21. On a quantitative basis, all of the 3-deoxyoctulosonate present in the cell envelope preparation was solubilized in hot sodium dodecyl sulfate and subsequently accounted for in its entirely in the isolated protein component. After incubation of the cell-wall particulate fraction of cells grown on [(3)H]glucosamine with UDP-[(14)C]galactose under conditions designed to measure galactosyl transferase activity, the isolated lipopolysaccharide protein contained all of the [(14)C]galactose that was incorporated during the incubation. We concluded that the lipopolysaccharide of this organism occurs in the outer cellenvelope membrane exclusively in the form of lipopolysaccharide protein.

Autoradiography↗
PubMed1968

Cell wall composition and virulence in Escherichia coli.

Uridine diphosphate galactose 4-epimerase and phosphomannose isomerase-deficient mutants of Escherichia coli O111:B4 were studied to test the hypothesis that in E. coli a specific relationship exists between O antigenicity, virulence, and capacity to resist phagocytosis. The first mutant, designated J-5, produces a cell wall lipopolysaccharide, the side chains of which do not contain galactose, glucose, N-acetylglucosamine, or colitose. The second mutant produces a cell wall lipopolysaccharide which lacks only colitose. The capacity of these various organisms to kill mice was strikingly different. E. coli O111 was 1000 times as virulent as J-5, and 100 times as virulent as L-2. The capacity of the organisms to kill mice was correlated with their ability to resist phagocytosis and to persist in the peritoneal cavity. The parent strain of O111 resisted phagocytosis by macrophages in vivo and polymorphonuclear leukocytes in vitro. The mutants did not, and the organism most deficient in the saccharide component of its LPS was most susceptible to phagocytosis and least virulent. These results were corroborated by growing the mutants in appropriately supplemented media which permitted the synthesis of complete LPS, reversed the susceptibility to phagocytosis, and restored virulence. Finally, serological reactivity was consistent with previous observations which had demonstrated that the O antigenicity of E. coli is determined by the saccharide composition of its cell wall lipopolysaccharide. Despite the difference in the capacity of the various log-phase organisms to kill mice when injected intraperitoneally, purified lipopolysaccharides extracted from them did not differ significantly in their capacity to kill or produce fever. Thus virulence was shown to be independent of endotoxin activity which in turn seemed to be unrelated to the saccharide composition of the cell wall LPS. Collectively, these data provide at least a partial molecular definition of virulence in E. coli by demonstrating that the presence or absence of specific sugars in its cell wall lipopolysaccharide is a determinant of its antiphagocytic capacity and its virulence.

Agglutination Tests↗