Division of labor in honey bee gut microbiota for plant polysaccharide digestion

Proc Natl Acad Sci U S A. 2019 Dec 17;116(51):25909-25916. doi: 10.1073/pnas.1916224116. Epub 2019 Nov 27.

Abstract

Bees acquire carbohydrates from nectar and lipids; and amino acids from pollen, which also contains polysaccharides including cellulose, hemicellulose, and pectin. These potential energy sources could be degraded and fermented through microbial enzymatic activity, resulting in short chain fatty acids available to hosts. However, the contributions of individual microbiota members to polysaccharide digestion have remained unclear. Through analysis of bacterial isolate genomes and a metagenome of the honey bee gut microbiota, we identify that Bifidobacterium and Gilliamella are the principal degraders of hemicellulose and pectin. Both Bifidobacterium and Gilliamella show extensive strain-level diversity in gene repertoires linked to polysaccharide digestion. Strains from honey bees possess more such genes than strains from bumble bees. In Bifidobacterium, genes encoding carbohydrate-active enzymes are colocated within loci devoted to polysaccharide utilization, as in Bacteroides from the human gut. Carbohydrate-active enzyme-encoding gene expressions are up-regulated in response to particular hemicelluloses both in vitro and in vivo. Metabolomic analyses document that bees experimentally colonized by different strains generate distinctive gut metabolomic profiles, with enrichment for specific monosaccharides, corresponding to predictions from genomic data. The other 3 core gut species clusters (Snodgrassella and 2 Lactobacillus clusters) possess few or no genes for polysaccharide digestion. Together, these findings indicate that strain composition within individual hosts determines the metabolic capabilities and potentially affects host nutrition. Furthermore, the niche specialization revealed by our study may promote overall community stability in the gut microbiomes of bees.

Keywords: amino acid; gut microbiota; honey bee; polysaccharide; symbiosis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacteria / classification
  • Bacteria / genetics
  • Bacteria / metabolism
  • Bees / microbiology*
  • Bees / physiology*
  • Bifidobacterium / genetics
  • Bifidobacterium / metabolism
  • Digestion*
  • Gammaproteobacteria / genetics
  • Gammaproteobacteria / metabolism
  • Gastrointestinal Microbiome / genetics
  • Gastrointestinal Microbiome / physiology*
  • Gastrointestinal Tract / microbiology
  • Gene Expression Regulation
  • Genome, Bacterial
  • Lactobacillus / genetics
  • Metagenome
  • Microbiota
  • Neisseriaceae / genetics
  • Plants / chemistry*
  • Pollen / chemistry
  • Polysaccharides / metabolism*

Substances

  • Polysaccharides