A sugary outer coating produced by probiotic bacteria could help them to survive in the good and may also offer clues to how they block some bacterial infections, say researchers.
The new study – published in the journal Proceedings of the National Academy of Sciences (PNAS) – could provide new insights into how probiotic bacteria provide positive health benefits. The research team, led by Professor Douwe van Sinderen and his colleagues at the Alimentary Pharmabiotic Centre in University College Cork, Ireland, revealed that the sugary outer coating (exocellular polysaccharide – EPS) of the probiotic Bifidobacterium breve UCC2003 could play a key role in its survival in the gut, its evasion of the immune system, and is also involved in reducing infection levels of gut pathogens.
“In this study we have shown that the outer EPS (exocellular polysaccharide) coating of Bifidobacterium breve UCC2003 protects the bacteria from acid and bile in the gut and shields the bacteria from the host immune response,” said van Sinderen.
“This research has led to an improved understanding of how probiotic bifidobacteria contribute to human and animal health, thereby will help to support their inclusion in functional foods,” he clarified.
van Sinderen said the observation that the EPS coating affected pathogen defence “represents an exciting new avenue for probiotic research.”
The authors noted that Bifidobacteria “comprise a significant proportion of the human gut microbiota.” As a result, several strains are currently used as therapeutic interventions, claiming various health benefits by acting as probiotics, they said.
However, van Sinderen and his team explained that the precise mechanisms by which such probiotics maintain their surroundings within their host – and consequently provide benefits – are not fully understood.
“We show that Bifidobacterium breve UCC2003 produces a cell surface-associated exopolysaccharide (EPS),” they wrote.
The surface EPS was found to provide stress tolerance against environmental conditions in the stomach and gut, and also produced a marked difference in host immune response.
“Strains producing surface EPS (EPS+) failed to elicit a strong immune response compared with EPS-deficient variants,” explained the researchers
EPS production was also shown to be linked to reduced colonization levels of the gut pathogen Citrobacter rodentium, they added.
van Sinderen and his colleagues said that the study data “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,” they added.
Source: Proceedings of the National Academy of Sciences (PNAS)
Published online ahead of print, doi: 10.1073/pnas.1115621109
“Bifidobacterial surface-exopolysaccharide facilitates commensal-host interaction through immune modulation and pathogen protection”
Authors: S. Fanning, L.J. Hall, M. Cronin, A. Zomer, J. MacSharry, D. Goulding, et al