Differences in fine arabinoxylan structures govern microbial selection and competition among human gut microbiota

Area of Science:

• Microbiome Research
• Dietary Fiber Science
• Metagenomics

Background:

• Dietary fibers influence microbiome composition.
• The impact of minor fiber structural variations on microbial communities is not well understood.

Purpose of the Study:

• To investigate how subtle differences in polysaccharide structure affect microbial community assembly, function, and metabolic responses.
• To test if variations in linkage complexity of sorghum arabinoxylans (SAXs) create distinct ecological niches.

Main Methods:

• In vitro sequential batch fecal fermentation using four fecal inocula over 7 days.
• Fermentation of two types of sorghum arabinoxylans (SAXs) with differing linkage complexities (RSAX and WSAX).
• Integrated multi-omics approach to analyze microbial community composition, genomes, and metabolic functions.

Main Results:

• RSAX supported higher species diversity (42 members) compared to WSAX (18-23 members).
• Distinct species-level genomes and metabolic outcomes were observed, with RSAX yielding more short-chain fatty acids and WSAX yielding more lactic acid.
• Key genera identified include Bacteroides, Bifidobacterium, and Lachnospiraceae, with varied carbohydrate active enzyme (CAZyme) gene profiles.

Conclusions:

• Fine polysaccharide structure exerts a deterministic selection effect on gut microbial consortia.
• Minor structural variations in dietary fibers can lead to significant differences in microbial community assembly and metabolic functions.