| By | Billion years ago |
| GOE | Great Oxidation Event |
| VOC | Volatile organic compound |
| OGBa | Operational group of Bacillus amyloliquefaciens |
| ABA | Abscisic acid |
| TMA | Trimethylamine |
| TMAO | Trimethylamine N-oxide |
| SCFA | Short-chain fatty acids |
| HPA | Hypothalamic–Pituitary–Adrenal (axis) |
| ACC | 1-aminocyclopropane-1-carboxylate |
| GABA | γ-aminobutyric acid |
| IgA | Immunoglobulin A |
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