A functionally augmented carbohydrate utilization locus from herbivore gut microbiota fueled by dietary β-glucans

Area of Science:

• Microbiology
• Biochemistry
• Genomics

Background:

• Members of the Bacteroidota phylum are crucial for mammalian health and metabolism.
• These bacteria possess polysaccharide utilization loci (PULs) enabling them to degrade recalcitrant dietary glycans.
• Understanding PUL functionality is key to comprehending gut microbiota's role in nutrition.

Purpose of the Study:

• To investigate the functional capacity of a polysaccharide utilization locus (PUL) from an herbivore gut bacterium.
• To compare the glycan processing capabilities of an herbivore PUL with a similar PUL found in the human gut microbiota.
• To elucidate the molecular adaptations responsible for expanded glycan utilization.

Main Methods:

• Comparative genomic analysis of PULs from herbivore and human gut bacteria.
• Biochemical characterization of carbohydrate-active enzymes within the herbivore PUL.
• Enzymatic assays to determine substrate specificity for β-glucans.

Main Results:

• The herbivore gut PUL, despite similar gene composition to human PULs, demonstrated broader functionality.
• This PUL efficiently processed linear and substituted β-1,3-glucans, in addition to mixed-linkage β-glucans.
• Key adaptations included specialized recognition proteins and a β-glucosidase targeting β(1,6)-glucosyl linkages.

Conclusions:

• The findings expand the known mechanisms of non-cellulosic β-glucan utilization by gut bacteria.
• Molecular adaptations in PULs contribute to functional diversity within the gut microbiota.
• This highlights intricate biochemical interactions and evolutionary adaptations in microbial glycan metabolism.