Utilization of four galactans by Bacteroides thetaiotaomicron A4 based on transcriptome

Abstract

Abstract The interaction between gut microbiota and polysaccharide is being paid more and more attention. Galactan is a kind of polysaccharide mainly composed of galactose, and it has been shown to play a significant role in regulating gut microbiota. Bacteroides thetaiotaomicron is considered as the best degrader of polysaccharides. The purpose of this paper was to investigate the utilization of four different galactans, including agarose, carrageenan, arabinogalactan, and glucofucogalactan, by our own isolated B. thetaiotaomicron A4. Samples of cultures grown on either four galactans groups or control groups were collected. The change of OD600, pH, and short‐chain fatty acids (SCFAs) during fermentation were determined, and growth curve and transcriptome of B. thetaiotaomicron A4 were studied. B. thetaiotaomicron A4 could utilize the four galactans and grew well on them, with carrageenan being most utilized, followed by arabinogalactan, glucofucogalactan, and agarose. SCFAs (mainly acetic acid and propionic acid) produced along with the decreased pH during fermentation. A large number of genes of B. thetaiotaomicron A4 were upregulated and functioned in different pathways during the degradation of the four galactans. The carbohydrate metabolism‐related pathways of B. thetaiotaomicron A4 were enriched after feeding the four galactans, although the specific pathways were different among four galactans groups. The different structural characteristics of four galactans required that B. thetaiotaomicron A4 could excrete corresponding enzymes to degrade them. These results help to understand the interaction between galactans and gut microbe.

Keywords

• Bacteroides thetaiotaomicron
• galactans
• short‐chain fatty acids
• transcriptome