Bifidobacterium breve UCC2003 Exopolysaccharide Modulates the Early Life Microbiota by Acting as a Potential Dietary Substrate.

Deborah Püngel,Jennifer Ketskemety,Ian J Colquhoun,Catherine Booth,Douwe Van Sinderen,Tamas Korcsmaros,Melissa Ae Lawson,Matthew J Dalby,Lindsay J Hall,Shabhonam Caim,Agatha Treveil

doi:10.3390/nu12040948

Abstract

Background: Bifidobacterium represents an important early life microbiota member. Specific bifidobacterial components, exopolysaccharides (EPS), positively modulate host responses, with purified EPS also suggested to impact microbe–microbe interactions by acting as a nutrient substrate. Thus, we determined the longitudinal effects of bifidobacterial EPS on microbial communities and metabolite profiles using an infant model colon system. Methods: Differential gene expression and growth characteristics were determined for each strain; Bifidobacterium breve UCC2003 and corresponding isogenic EPS-deletion mutant (B. breve UCC2003del). Model colon vessels were inoculated with B. breve and microbiome dynamics monitored using 16S rRNA sequencing and metabolomics (NMR). Results: Transcriptomics of EPS mutant vs. B. breve UCC2003 highlighted discrete differential gene expression (e.g., eps biosynthetic cluster), though overall growth dynamics between strains were unaffected. The EPS-positive vessel had significant shifts in microbiome and metabolite profiles until study end (405 h); with increases of Tyzzerella and Faecalibacterium, and short-chain fatty acids, with further correlations between taxa and metabolites which were not observed within the EPS-negative vessel. Conclusions: These data indicate that B. breve UCC2003 EPS is potentially metabolized by infant microbiota members, leading to differential microbial metabolism and altered metabolite by-products. Overall, these findings may allow development of EPS-specific strategies to promote infant health.

Highlights

Members from the genus Bifidobacterium represent one of the dominant bacterial groups in the early life gut microbiota, with high levels associated with improved infant health [1,2,3,4,5]
Pure bacterial cultures were subjected to Transmission Electron Microscopy (TEM) to visualize the presence and absence of EPS prior to model colon experiments
Images indicated EPS-positive B. breve UCC2003 bacteria had a thicker and differentially stained cell wall, in contrast to the EPS-negative strain (i.e. B. breve UCC2003del) which is in line with previously published data [16]

Summary

Introduction

Members from the genus Bifidobacterium represent one of the dominant bacterial groups in the early life gut microbiota, with high levels associated with improved infant health [1,2,3,4,5]. The introduction of solid food at weaning marks a transition into a more complex microbiome, with a concurrent reduction in Bifidobacterium levels, likely due to the loss of milk as a sole dietary source During these phases of significant dietary change, there is a shift in bifidobacterial species and strains, which may link to the wider repertoire of enzymes capable of digesting a more ‘adult’. Conclusions: These data indicate that B. breve UCC2003 EPS is potentially metabolized by infant microbiota members, leading to differential microbial metabolism and altered metabolite by-products. Overall, these findings may allow development of EPS-specific strategies to promote infant health

Methods

Results

Discussion

Conclusion