Human gut microbes use multiple transporters to distinguish vitamin B₁₂ analogs and compete in the gut

Cell Host Microbe. 2014 Jan 15;15(1):47-57. doi: 10.1016/j.chom.2013.12.007.


Genomic and metagenomic sequencing efforts, including human microbiome projects, reveal that microbes often encode multiple systems that appear to accomplish the same task. Whether these predictions reflect actual functional redundancies is unclear. We report that the prominent human gut symbiont Bacteroides thetaiotaomicron employs three functional, homologous vitamin B₁₂ transporters that in at least two cases confer a competitive advantage in the presence of distinct B₁₂ analogs (corrinoids). In the mammalian gut, microbial fitness can be determined by the presence or absence of a single transporter. The total number of distinct corrinoid transporter families in the human gut microbiome likely exceeds those observed in B. thetaiotaomicron by an order of magnitude. These results demonstrate that human gut microbes use elaborate mechanisms to capture and differentiate corrinoids in vivo and that apparent redundancies observed in these genomes can instead reflect hidden specificities that determine whether a microbe will colonize its host.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antibiosis / physiology
  • Bacterial Outer Membrane Proteins / classification
  • Bacterial Outer Membrane Proteins / genetics*
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacteroides / genetics
  • Bacteroides / metabolism
  • Biological Transport
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / classification
  • Escherichia coli Proteins / genetics*
  • Escherichia coli Proteins / metabolism
  • Gastrointestinal Tract / microbiology*
  • Gene Expression Regulation, Bacterial*
  • Genome, Bacterial*
  • Humans
  • Membrane Transport Proteins / classification
  • Membrane Transport Proteins / genetics*
  • Membrane Transport Proteins / metabolism
  • Mice
  • Microbiota*
  • Phylogeny
  • Species Specificity
  • Symbiosis / physiology
  • Vitamin B 12 / analogs & derivatives
  • Vitamin B 12 / metabolism*


  • Bacterial Outer Membrane Proteins
  • BtuB protein, E coli
  • Escherichia coli Proteins
  • Membrane Transport Proteins
  • Vitamin B 12