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Factors contributing to the competitiveness of Lactobacillus reuteri in sourdough and rodent gut Open Access


Other title
Two-component system
Acid resistance
Comparative genomic hybridization
Biofilm formation
Double crossover method
Lactobacillus reuteri
Glutamate decarboxylase
Type of item
Degree grantor
University of Alberta
Author or creator
Su, Shu-Wei
Supervisor and department
Gänzle, Michael (Agricultural, Food and Nutritional Science)
Examining committee member and department
Stuart, David (Biochemistry)
Giffard, Philip (Menzies School of Health Research, Australia)
McMullen, Lynn (Agricultural, Food and Nutritional Science)
Stothard, Paul (Agricultural, Food and Nutritional Science)
Department of Agricultural, Food and Nutritional Science

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Lactobacillus reuteri is a common organism in cereal-based foods and a gut symbiont in humans and animals, yet the molecular mechanisms allowing its persistence in various niches are not well understood. L. reuteri LTH2584 produces reutericyclin and persists in industrial sourdoughs, where acidic conditions during fermentation cause acid stress to organisms. Another strain, L. reuteri 100-23, colonizes the murine forestomach, where this type of lactobacilli contributes to digesta preservation through acid production. L. reuteri LTH2584 and 100-23 were studied to gain an understanding of the phylogenetic relationship between these two isolates, as well as the acid resistance mechanisms and the two-component systems that contribute to the persistence of L. reuteri in sourdough and the murine gut. Analysis of genomic content revealed a close evolutionary relationship between the L. reuteri isolates from sourdough and rodent gut. In addition, a novel double crossover method was developed to generate isogenic deletion mutants for the evaluation of competitiveness, while the acid resistance mechanism was assessed by disruption of glutamate decarboxylase (gadB) in L. reuteri 100-23. Glutamate decarboxylase enhanced the ability of L. reuteri to adapt to both acidic environments (in vitro) and sourdough fermentations (in vivo) by decarboxylation of glutamate to γ-aminobutyric acid. Biofilm formation may depend on the cross-communication of the hk430 and cemAKR operons. Several osmoregulatory genes that may also be associated with cell envelope architecture and cell morphology were also identified.
License granted by Shu-Wei Su ( on 2011-09-23T04:13:18Z (GMT): Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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