Molecular characterization of the starch utilitization system of Bacteroides thetaiotaomicron
Reeves, Andrew Robert
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/23141
Description
Title
Molecular characterization of the starch utilitization system of Bacteroides thetaiotaomicron
Author(s)
Reeves, Andrew Robert
Issue Date
1996
Doctoral Committee Chair(s)
Salyers, Abigail A.
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
Language
eng
Abstract
Bacteroides spp. are obligately anaerobic Gram-negative bacilli that reside in high numbers in the colons of humans and animals. It has been estimated that Bacteroides spp. constitute as high as 30% of all colonic isolates. Since mono- and di-saccharides are efficiently absorbed in the small intestine, Bacteroides spp. are probably using polysaccharides as their main sources of carbon and energy. One of the reasons that Bacteroides spp. are so successful at colonizing the colon may be due to the nutritional versatility exhibited by the numerically predominant colonic Bacteroides spp., namely, B. thetaiotaomicron, B. vulgatus, and B. uniformis. All these species are able to ferment a wide variety of dietary polysaccharides as well as host-derived mucopolysaccharides. Another possible reason for their success at colonizing the colon may be due to the intrinsic nature of the way Bacteroides' polysaccharide utilization systems work. Instead of taking a divide-and-conquer approach, that is, secreting extracellular polysaccharidases into the surrounding medium and translocating the breakdown products of enzymes through porins, Bacteroides spp. appear first to bind the polysaccharide at the cell surface and then to transport the molecule into the periplasm, where the majority of the polysaccharide-hydrolyzing enzymes are located. Nonetheless, the preponderance of the starch-hydrolyzing activity is within the cell, and until the precise location and topology of the outer membrane enzymes are found, the current model favors translocation across the outer membrane by a starch binding receptor. In any case, this general polysaccharide uptake strategy (substrate-sequestration) would confer a selective advantage to Bacteroides spp. in competition with those species of colonic bacteria that secrete extracellular enzymes, who most likely lose a large amount of potential nutritional sources to nearby competitors. My work centered on the characterization of several outer membrane proteins (OMPs) involved in the early steps of the starch utilization process with the broad aims of determining the functional roles of the OMPs and developing a general working model of starch utilization in B. thetaiotaomicron, particularly with regard to the early steps.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
