Cell Host & Microbe
Volume 22, Issue 4, 11 October 2017, Pages 494-506.e8
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Article
A Subset of Polysaccharide Capsules in the Human Symbiont Bacteroides thetaiotaomicron Promote Increased Competitive Fitness in the Mouse Gut

https://doi.org/10.1016/j.chom.2017.08.020Get rights and content
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Highlights

  • B. thetaiotaomicron dynamically changes its capsular polysaccharides (CPSs) in vivo

  • One capsule, CPS5, provides the most advantage in the presence of adaptive immunity

  • The ability to express multiple CPS types promotes survival during antibiotic stress

  • CPS5 is one of the most prevalent B. thetaiotaomicron CPS in human samples

Summary

Capsular polysaccharides (CPSs) play multiple roles in protecting bacteria from host and environmental factors, and many commensal bacteria can produce multiple capsule types. To better understand the roles of different CPSs in competitive intestinal colonization, we individually expressed the eight different capsules of the human gut symbiont Bacteroides thetaiotaomicron. Certain CPSs were most advantageous in vivo, and increased anti-CPS immunoglobulin A correlated with increased fitness of a strain expressing one particular capsule, CPS5, suggesting that it promotes avoidance of adaptive immunity. A strain with the ability to switch between multiple capsules was more competitive than those expressing any single capsule except CPS5. After antibiotic perturbation, only the wild-type, capsule-switching strain remained in the gut, shifting to prominent expression of CPS5 only in mice with intact adaptive immunity. These data suggest that different capsules equip mutualistic gut bacteria with the ability to thrive in various niches, including those influenced by immune responses and antibiotic perturbations.

Keywords

capsular polysaccharide
Bacteroides
immune response
IgA
diet
microbiota
microbiome

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