Little is known about how members of the indigenous microflora interact with their mammalian hosts to establish mutually beneficial relationships. We have used a gnotobiotic mouse model to show that Bacteroides thetaiotaomicron, a component of the intestinal microflora of mice and humans, uses a repressor, FucR, as a molecular sensor of L-fucose availability. FucR coordinates expression of an operon encoding enzymes in the L-fucose metabolic pathway with expression of another locus that regulates production of fucosylated glycans in intestinal enterocytes. Genetic and biochemical studies indicate that FucR does this by using fucose as an inducer at one locus and as a corepressor at the other locus. Coordinating this commensal's immediate nutritional requirements with production of a host-derived energy source is consistent with its need to enter and persist within a competitive ecosystem.

Original languageEnglish
Pages (from-to)9833-9838
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number17
StatePublished - Aug 17 1999


  • Bacteroides thetaiotaomicron
  • Epithelial fucosylated glycan synthesis
  • Germ-free mice
  • Host-microbial cross-talk
  • Transcriptional repressors


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