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Genetic variation of the SusC/SusD homologs from a polysaccharide utilization locus underlies divergent fructan specificities and functional adaptation in Bacteroides thetaiotaomicron strains

Lookup NU author(s): Carl Morland, Dr David Bolam

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2018 Joglekar et al. Genomic differences between gut-resident bacterial strains likely underlie significant interindividual variation in microbiome function. Traditional methods of determining community composition, such as 16S rRNA gene amplicon sequencing, fail to capture this functional diversity. Metagenomic approaches are a significant step forward in identifying strain-level sequence variants; however, given the current paucity of biochemical information, they too are limited to mainly lowresolution and incomplete functional predictions. Using genomic, biochemical, and molecular approaches, we identified differences in the fructan utilization profiles of two closely related Bacteroides thetaiotaomicron strains. B. thetaiotaomicron 8736 (Bt- 8736) contains a fructan polysaccharide utilization locus (PUL) with a divergent susC/ susD homolog gene pair that enables it to utilize inulin, differentiating this strain from other characterized Bt strains. Transfer of the distinct pair of susC/susD genes from Bt-8736 into the noninulin using type strain B. thetaiotaomicron VPI-5482 resulted in inulin use by the recipient strain, Bt(8736-2). The presence of the divergent susC/susD gene pair alone enabled the hybrid Bt(8736-2) strain to outcompete the wild-type strain in vivo in mice fed an inulin diet. Further, we discovered that the susC/susD homolog gene pair facilitated import of inulin into the periplasm without surface predigestion by an endo-acting enzyme, possibly due to the short average chain length of inulin compared to many other polysaccharides. Our data builds upon recent reports of dietary polysaccharide utilization mechanisms found in members of the Bacteroides genus and demonstrates how the acquisition of two genes can alter the functionality and success of a strain within the gut.

Publication metadata

Author(s): Joglekar P, Sonnenburg ED, Higginbottom SK, Earle KA, Morland C, Shapiro-Ward S, Bolam DN, Sonnenburg JL

Publication type: Article

Publication status: Published

Journal: mSphere

Year: 2018

Volume: 3

Issue: 3

Online publication date: 23/04/2018

Acceptance date: 13/04/2018

Date deposited: 20/06/2018

ISSN (electronic): 2379-5042

Publisher: American Society for Microbiology

URL: https://doi.org/10.1128/mSphereDirect.00185-18

DOI: 10.1128/mSphereDirect.00185-18

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