Bifidobacterial surface-exopolysaccharide facilitates commensal-host interaction through immune modulation and pathogen protection

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.

Exploring the role of the microbiota member Bifidobacterium in modulating immune-linked diseases

“…Further investigation is required to provide mechanistic correlation, but we hypothesise that bifidobacteria may potentially modulate foetal immune development at the very first stages of life. and links to specific bifidobacteria molecules [40,41], such as pili and exopolysaccharide (EPS), on immune responses [5,42,43]. However, it is apparent that the bifidobacteria-immune field requires a greater number of investigations detailing key mechanistic targets and pathways in different immune compartments and immune cell types.…”

“…infantis 35624 to modulate innate immune cells, such as neutrophils, macrophages, and peripheral monocytes [5,43]. An EPS deletion mutant in B. breve UCC2003 induced more pro-inflammatory cytokine secretion from splenocytes and also increased the number of Ly6G + neutrophils, F4/80 + macrophages, DX5 + /CD3 + NK cells, and CD19 + B cells in the spleen of treated mice compared with mice treated with the wild-type strain [5]. Similarly, an EPS deletion mutant of B. longum subsp.…”

“…Bifidobacteria have been used for many years as supplements to promote host wellbeing, as their presence, including the high levels observed in infants and stable levels in adults, is associated with a 'healthy' state. These bacteria are particularly effective at protecting against infectious diseases [4][5][6][7] and modulating immune responses [7,8]. This review discusses Bifidobacterium across the life course, and focuses on species and specific strains that have been studied in the context of immune modulation and treatment of disease.…”

Faecalibacterium prausnitzii strain HTF-F and its extracellular polymeric matrix attenuate clinical parameters in DSS-induced colitis

“…Here we showed that strain HTF-F produces an extracellular polymeric matrix (EPM) that might provide an advantage to colonization in vivo through intercellular aggregation and biofilm formation. As bacterial EPMs are common components of biofilm matrices and have been previously shown to have immunomodulatory effects [8][9][10], we tested the EPM of strain HTF-F for its potential anti-inflammatory effects in the DSS colitis model. Additionally, the immunomodulatory effects of the EPM were investigated using immature dendritic cells derived ex vivo from human monocytes and mouse bone marrow cells.…”

Evaluation of bifidobacterial adhesion to acidic sugar chains of porcine colonic mucins

“…1) In some studies, consumption of specific bifidobacteria has been shown to be associated with immune modulation, 2) protection against pathogens, 2,3) and anti-aging effects. 4) Therefore, several Bifidobacterium strains are commonly used as probiotics.…”