Genetic characterization of the mucopolysaccharide utilization system of Bacteroides thetaiotaomicron
Cheng, Qiong
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Permalink
https://hdl.handle.net/2142/21123
Description
Title
Genetic characterization of the mucopolysaccharide utilization system of Bacteroides thetaiotaomicron
Author(s)
Cheng, Qiong
Issue Date
1994
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, Molecular
Biology, Genetics
Biology, Microbiology
Language
eng
Abstract
Polysaccharides are a major source of carbon and energy for the bacteria that normally reside in the human colon. The finding that some of the major colonic species such as Bacteroides thetaiotaomicron can utilize host-derived polysaccharides as well as dietary polysaccharides raised the question of whether host-derived polysaccharides might be an important source of polysaccharides for some colonic bacteria. To address this question, I have taken a genetic approach investigating the mechanism of host-derived mucopolysaccharide utilization and determining the importance of mucopolysaccharides for the survival of Bacteroides in the human colon.
My investigation began with the characterization of three Tn4351-generated mutants of B. thetaiotaomicron that were deficient in utilization of one or more of the host-derived mucopolysaccharides: chondroitin sulfate, hyaluronic acid and heparin. Mutants CS3 and 46-1 were unable to utilize chondroitin sulfate and heparin (CS$\sp-$HP$\sp-$). Mutations in CS3 and 46-1 mapped to the same gene: chuR. chuR might encode a positive regulatory protein that controls the expression of a subset of mucopolysaccharide utilization genes. chuR is the first known regulatory link between CS utilization and HP utilization. Expression of chuR is important for colonization in vivo. The third mutant, CS4, was unable to utilize chondroitin sulfate and hyaluronic acid (CS$\sp-$HA$\sp-$). CS4 locus might encode an outer membrane protein that is essential for transporting CS and HA across the outer membrane. In an attempt to determine what genes were controlled by ChuR, I isolated two classes of intergenic suppressors of a null chuR mutation. Preliminary characterization of these suppressors indicated that there was more than one mechanism for suppressing the chuR null mutation. It also suggested that CS$\sp-$HP$\sp-$ phenotype might be detrimental in vivo.
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