Abstract:
:Bifidobacteria comprise a significant proportion of the human gut microbiota. Several bifidobacterial strains are currently used as therapeutic interventions, claiming various health benefits by acting as probiotics. However, the precise mechanisms by which they maintain habitation within their host and consequently provide these benefits are not fully understood. Here we show that Bifidobacterium breve UCC2003 produces a cell surface-associated exopolysaccharide (EPS), the biosynthesis of which is directed by either half of a bidirectional gene cluster, thus leading to production of one of two possible EPSs. Alternate transcription of the two opposing halves of this cluster appears to be the result of promoter reorientation. Surface EPS provided stress tolerance and promoted in vivo persistence, but not initial colonization. Marked differences were observed in host immune response: strains producing surface EPS (EPS(+)) failed to elicit a strong immune response compared with EPS-deficient variants. Specifically, EPS production was shown to be linked to the evasion of adaptive B-cell responses. Furthermore, presence of EPS(+) B. breve reduced colonization levels of the gut pathogen Citrobacter rodentium. Our data thus assigns a pivotal and beneficial role for EPS in modulating various aspects of bifidobacterial-host interaction, including the ability of commensal bacteria to remain immunologically silent and in turn provide pathogen protection. This finding enforces the probiotic concept and provides mechanistic insights into health-promoting benefits for both animal and human hosts.
journal_name
Proc Natl Acad Sci U S Aauthors
Fanning S,Hall LJ,Cronin M,Zomer A,MacSharry J,Goulding D,Motherway MO,Shanahan F,Nally K,Dougan G,van Sinderen Ddoi
10.1073/pnas.1115621109subject
Has Abstractpub_date
2012-02-07 00:00:00pages
2108-13issue
6eissn
0027-8424issn
1091-6490pii
1115621109journal_volume
109pub_type
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