Table 3.
Metabolites/neurotransmitters produced by the gut microbiome.
| Metabolite/neurotransmitter | Microbiota species | References |
|---|---|---|
| Acetylcholine | Lactobacillus spp. | Kawashima et al. (2007) |
| Cannabinoid anandamide (AEA) | Lactobacillus johnsonii and Lactobacillus reuteri | Petrie et al. (2021) |
| Dopamine (DA) | Lactobacillus spp. | Kawashima et al. (2007), Ozogul (2011), Kuley et al. (2012), and Holzer and Farzi (2014) |
| Gamma aminobutyric acid (GABA) | Lactobacillus spp. | Takanaga et al. (2001), Bravo et al. (2011), Barrett et al. (2012), Janik et al. (2016), and Kim and Shin (2018) |
| Bifidobacterium genus, Lactobacillus spp. | Socała et al. (2021) | |
| Lactobacillus brevis, Bifidobacterium dentium | Barrett et al. (2012) | |
| Histamine | Lactobacillus spp. | Landete et al. (2008) and Hemarajata et al. (2013) |
| ↓ Proinflammatory cytokine TNF-α | Lactobacillus spp. | Thomas et al. (2012) |
| Serotonin (5-HT) | Streptococcus spp., Enterococcus spp., Escherichia spp. | Dinan et al. (2013) |
| Escherichia spp., Hafnia spp., Klebsiella spp., Lactobacillus spp., Morganella spp., Streptococcus spp. | O’Mahony et al. (2015) | |
| Short-chain fatty acids (SCFAs): acetic acid, butyric acid, propionic acid | Lactobacillus spp., Bacteroides spp., Clostridiae spp. | Turnbaugh et al. (2009), Collins et al. (2015), Bull-Larsen and Mohajeri (2019), and Park and Im (2020) |
| Lactobacillus brevis and Bifidobacterium dentium | Barrett et al. (2012) | |
| Tryptophan | ↑ Concentrations in the blood of GF male animals suggest a humoral mechanism of the microbiota influencing CNS serotonergic neurotransmission. | Cryan and Dinan (2012) |