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UBC Theses and Dissertations

Structural investigation and bacteriophage degradation of bacterial polysaccharides Karunaratne, Desiree Nedra


Seventy eight serologically distinct strains of Klebsiella bacteria are known to exist. The capsular polysaccharide surrounding the bacterial cell of these pathogenic Enterobacteria is of immunological significance. Structures of the capsular polysaccharides of nearly sixty seven strains of Klebsiella have been established, and each one found to be unique. The structures of the K antigens from Klebsiella, serotypes K67 and K80 are presented as a contribution to the continuing program of elucidation of the chemical structures of these antigens in an attempt to explain their immunological responses. Chemical methods of structural elucidation were employed and the following two structures were obtained. [formula omitted] The polysaccharide from K67 was unique among the Klebsiella K antigens in having a four-plus-two-plus-one repeating-unit (indicating a branch on a side chain), while K80 was unique as it was the first instance that a pyruvic acetal was found on a terminal rhamnose unit. The importance of bacteriophage-borne enzymes in the generation of single repeating-units containing labile substituents is demonstrated. Klebsiella K44 polysaccharide was degraded using a crude solution of Φ44 bacteriophage. The oligosaccharides obtained were crucial in the determination of the position of the 0-acetate group. In the case of the polysaccharide from Klebsiella K26, the degradation performed using a crude solution of Φ26 bacteriophage resulted in the isolation of a single repeating-unit containing a pyruvic acetal together with an oligosaccharide corresponding to a single repeating-unit devoid of its terminal pyruvate containing sugar. The structures of these compounds which are as follows, were useful in further confirmation of the structures of the original polysaccharides. [formula omitted] Escherichia coli. another pathogenic Enterobacteria possessing immunologically significant K antigens, has been found to contain capsular polysaccharides bearing a strong resemblance to those of Klebsiella. Recently it was discovered that some strains of E. coli contained K antigens comprising amino sugars. A preliminary study on the chemical behaviour of amino sugars, and chemical methods of structure elucidation of such polysaccharides have been included in an appendix as this has been a new area of research in this laboratory. An appendix containing compilations of the cross-reactions, known structures, and chemotypes of the Klebsiella K antigens has also been included.

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