SIALIC ACIDS (N,7-O-DIACETYLNEURAMINIC ACID AND N-ACETYLNEURAMINIC ACID) IN ESCHERICHIA COLI II. : Their Presence on the Cell Wall Surface and Relationship to K Antigen

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DeWitt, Charles W. (The Upjohn Co., Kalamazoo, Mich.) and Elizabeth A. Zell. Sialic acids (N,7-O-diacetylneuraminic acid and N-acetylneuraminic acid) in Escherichia coli. II. Their presence on the cell wall surface and relationship to K antigen. J. Bacteriol. 82:849–856. 1961.—Sialic acids obtained from Escherichia coli by weak acid hydrolysis are shown to be released from the extreme-surface, lipoprotein layer of the cell. Hydrolysis does not lyse the cells nor release cell walls. Hydrolysates do not contain compounds such as α, ε-diaminopimelic acid or N-acetylmuramic acid, normally associated with cell walls. The surface material is released in a relatively homogeneous form by simple incubation of live cells in an acidic buffer and is susceptible to hydrolysis by viral neuraminidase, although untreated live cells will not serve as substrate. As this surface material resembles, in its initial rate of reaction with neuraminidase, human urinary mucoprotein, the sialic acid is presumably present as an α-ketoside. Colominic acid is insusceptible under the same conditions. Although there is good correlation of the occurrence of sialic acids with the E. coli capsular antigen, K1, specific release of sialic acid from K1 antigen with neuraminidase does not lessen its haptenic activity as measured by inhibition of specific agglutination.

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