Neurotransmitter Profiles Are Altered in the Gut and Brain of Mice Mono-Associated with Bifidobacterium dentium

Biomolecules. 2021 Jul 23;11(8):1091. doi: 10.3390/biom11081091.


Background: Accumulating evidence indicates that the gut microbiota can synthesize neurotransmitters as well as impact host-derived neurotransmitter levels. In the past, it has been challenging to decipher which microbes influence neurotransmitters due to the complexity of the gut microbiota.

Methods: To address whether a single microbe, Bifidobacterium dentium, could regulate important neurotransmitters, we examined Bifidobacteria genomes and explored neurotransmitter pathways in secreted cell-free supernatant using LC-MS/MS. To determine if B. dentium could impact neurotransmitters in vivo, we mono-associated germ-free mice with B. dentium ATCC 27678 and examined fecal and brain neurotransmitter concentrations.

Results: We found that B. dentium possessed the enzymatic machinery to generate γ-aminobutyric acid (GABA) from glutamate, glutamine, and succinate. Consistent with the genome analysis, we found that B. dentium secreted GABA in a fully defined microbial media and elevated fecal GABA in B. dentium mono-associated mice compared to germ-free controls. We also examined the tyrosine/dopamine pathway and found that B. dentium could synthesize tyrosine, but could not generate L-dopa, dopamine, norepinephrine, or epinephrine. In vivo, we found that B. dentium mono-associated mice had elevated levels of tyrosine in the feces and brain.

Conclusions: These data indicate that B. dentium can contribute to in vivo neurotransmitter regulation.

Keywords: Bifidobacteria; GABA; LC-MS/MS; gut microbiome; gut–brain axis; neurotransmitters.

Publication types

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

MeSH terms

  • Animals
  • Bifidobacteriales Infections / metabolism
  • Bifidobacterium / metabolism*
  • Brain / metabolism
  • Calibration
  • Chromatography, Liquid
  • Gastrointestinal Microbiome
  • Genome
  • Intestines / pathology
  • Male
  • Mice
  • Microbiota
  • Neurotransmitter Agents / metabolism*
  • Tandem Mass Spectrometry
  • Tyrosine / metabolism


  • Neurotransmitter Agents
  • Tyrosine

Supplementary concepts

  • Bifidobacterium dentium