A Subset of Polysaccharide Capsules in the Human Symbiont Bacteroides thetaiotaomicron Promote Increased Competitive Fitness in the Mouse Gut

Abstract

Summary Capsular polysaccharides (CPS) 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 CPS in competitive intestinal colonization, we individually expressed the eight different capsules of the human gut symbiont Bacteroides thetaiotaomicron. Certain CPS were most advantageous in vivo, and increased anti-CPS IgA 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.

In Vitro Analysis of Virulence Factors Which Enhances Pathogenic Potential With an Emphasis on Biofilm Formation in Bacteroides Fragilis Group.

“…A study reported a particular capsular polysaccharides (CPS5) was found in human samples which can produce multiple capsule types to survive antibiotic therapy. (Porter et al,2017) In our study 54 (74%) strains produced capsule.…”

Parabacteroides distasonis Alleviates Obesity and Metabolic Dysfunctions via Production of Succinate and Secondary Bile Acids

“…Bacterial cellular components (anaerobic lysate, polysaccharide capsules, or outer-membrane pili-like protein) play significant roles in the cross talk between gut symbionts and the host (Plovier et al, 2017;Porter et al, 2017;Neff et al, 2016). Amuc_1100*, a thermostable outer-membrane protein of A. muciniphila, reportedly possesses beneficial effects on reducing fat mass and improving metabolic syndrome in dietinduced obese mice (Plovier et al, 2017).…”

Adaptive evolution within the gut microbiome of individual people

“…The discrepancy in signals between timescales implies that the selective forces acting on these genes are not constant and raises the possibility that adaptive mutations occurring in vivo may incur collateral fitness costs in the context of other selective forces 41,42 . This notion of competing selective forces is echoed by the well-described invertible promoters of B. fragilis, which enable rapid alternation between different outer-membrane presentations 43,44 . Interestingly, the invertible promoters control the same major pathways that we identified as undergoing positive selection (capsule synthesis and polysaccharide importers) 43,45 .…”