Assessing the Potential Role of Human Colonic Bacteroides Species in the Catabolism of Two Dietary Polymers in Vivo
McCarthy, Robert Eugene
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https://hdl.handle.net/2142/71191
Description
Title
Assessing the Potential Role of Human Colonic Bacteroides Species in the Catabolism of Two Dietary Polymers in Vivo
Author(s)
McCarthy, Robert Eugene
Issue Date
1987
Department of Study
Microbiology
Discipline
Microbiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Microbiology
Abstract
Bacteroides, a genus of Gram negative obligately anaerobic bacteria, are among the most numerous organisms in the human colon. This genus contains the most versatile degraders of polysaccharides among the colonic microflora. Polysaccharides derived from the diet along with mucopolysaccharides and mucins are probably the major carbon and energy sources for these saccharolytic bacteria. However, it has been difficult to test this hypothesis because the complexity of the colonic ecosystem has precluded efforts to follow polysaccharide utilization by a particular species in the colon. Thus, the goal of my project was to try and develop a new methodology by which the in vivo catabolic activities of a colonic bacterial species could be followed.
Preliminary studies indicated that amylase and polygalacturonase activities were two of the highest polysaccharidase activities recovered from the bacterial fraction of fecal specimens. Moreover, Bacteroides spp. can utilize pectin (PGA) and starch when grown on laboratory medium in pure culture. These two polysaccharide-degrading systems were characterized in Bacteroides. The PGA-degrading enzymes, a PGA lyase and a PGA hydrolase, were found to be inducible and cell-associated. These enzymes were characterized and partially purified from B. thetaiotaomicron. The PGA lyases from the other major Bacteroides spp. which can utilize PGA were compared to the PGA lyase produced by B. thetaiotaomicron and a PGA lyase recovered from fecal specimens.
Similarly, starch is another potential carbon and energy source for Bacteroides. B. vulgatus produces an $\alpha$- glucosidase when grown on maltose, amylose, and amylopectin. Antibody was made to the B. vulgatus purified $\alpha$-glucosidase and used on Western blots to determine if a fecal $\alpha$-glucosidase of similar properties was produced by B. vulgatus. Finally, the possibility of using germfree mice as potential animal models for assessing factors that affect polysaccharide utilization in vivo is discussed.
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