Ecological importance of cross-feeding of the intermediate metabolite 1,2-propanediol between bacterial gut symbionts

• Author / Creator

  Cheng, Christopher

• Cross-feeding of intermediary metabolites such as 1,2-propanediol (1,2-PDO) has been proposed to have an important role in the establishment of syntrophic interactions among gut symbionts, but its ecological importance has not been empirically established. This thesis shows that growth of L. reuteri ATCC PTA 6475 in media is enhanced through 1,2-PDO produced by Bifidobacterium breve UCC2003 and Escherichia coli MG1655 from substrates (fucose and rhamnose) that cannot be utilized by L. reuteri. This syntrophy is strictly dependent on the pdu-cbi-cob-hem gene (pdu) cluster in L. reuteri, which encodes for the ability to utilize 1,2-PDO as an electron acceptor to enhance their growth rates, and it requires the L-fucose permease (fucP) gene in B. breve, which is needed for the metabolite formation of 1,2-PDO from fucose. Experiments in gnotobiotic mice revealed that ecological performance of L. reuteri ATCC PTA 6475 in the gastrointestinal tract was enhanced through trophic interactions with B. breve UCC2003. Use of isogenic mutants confirmed that this advantage was dependent on the pdu cluster in L. reuteri and fucP in B. breve, indicating that this interaction is specifically based on 1,2-PDO. These findings establish the ecological importance of syntrophic relationships based on 1,2-PDO for the fitness of a bacterial symbiont in the vertebrate gut.
  Cross-feeding of 1,2-PDO between non-pathogenic members of the gut microbiota has been inferred from the metabolic pathways of gut microbes and metagenomic analyses, but its ecological ramifications remain unexplored. In this thesis, we determined the importance of 1,2-PDO cross-feeding using isogenic mutants of both the bacterium that produced the metabolic intermediate (Bifidobacterium breve) and the species that utilized it (Lactobacillus reuteri). The results indicate that trophic interactions based on 1,2-PDO are important for the ecophysiology of the gut as they influence both growth and in vivo performance of the microbe able to utilize the intermediate. The findings from this study improve our understanding of how metabolic networks establish within the gut microbiota and are relevant for the design of strategy to modulate gut ecosystems, which might benefit from the use of mixtures of bacterial strains that establish syntrophic interactions in probiotic applications.

• Subjects / Keywords

  • Lactobacillus
  • cross-feeding
  • reuteri
  • 1,2-propanediol

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-4ner-vs56

• License

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