Bacteriophage T4D Receptor and the Escherichia coli Cell Wall Structure: Binding of Endotoxin-Like Particles to the Cell Wall

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A variety of degradative treatments have been used to investigate the nature of the structure and components of the cell walls of Escherichia coli B. The binding and localization of the endotoxin-like particles found on the cell walls were of special interest because some of them are associated with the site where the inner tail tube of bacteriophage T4D penetrates the cell wall. Modified cell walls were obtained by heating a suspension of bacterial cells originally in 0.1 M phosphate, pH 7.0, after the addition of 12.5 M NaOH to a final concentration of 0.25 M. With regard to the endotoxin-like particles, it was found that: (i) at least part of them still remained bound to the modified cell wall after the alkali treatment; (ii) the subsequent incubation of alkali-treated cell walls with lysozyme destroyed the bacterial form and released a complex of endotoxin-like particles together with a fibrous material; (iii) on the other hand, treatment with 45% phenol at 70°C removed the endotoxin-like particles from the surface of the alkali-treated cell walls, but most of the fibrous material was left on the cell wall; and (iv) incubation of alkali-treated cell walls with 5 mM ethylenediaminetetraacetic acid at 20°C also removed the endotoxin-like particles, but did not disrupt the rodlike bacterial form. However, if the ethylenediaminetetraacetic acid treatment was performed at 55°C, the bacterium-like form was destroyed. These differential sensitivities to ethylenediaminetetraacetic acid suggested that loosely bound divalent metal ions normally hold these endotoxin-like particles on the cell wall surface, but that probably more tightly bound metal ions are involved in the determination of cell shape. Analysis of the protein components of the alkalitreated cell walls showed that only one protein was present in significant amounts, and this protein had an electrophoretic mobility similar to that of the Braun lipoprotein. This protein was released from the alkali-treated cell walls upon heating with 2% sodium dodecyl sulfate at 100°C. Phospholipids were also absent from this structure. The distribution of the remaining cell wall components on the alkali-treated cell walls is discussed.

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