TABLE 4.
Overview of some of the most important molecular mechanisms of probiotics
| Type of action | Mode of action | Molecule(s)/structure(s)/adjustment | Example(s) | Reference(s) |
|---|---|---|---|---|
| Competition | Adhesion sites and receptors | Pili or fimbriae | SpaCBA pili in L. rhamnosus GG | 173, 187 |
| Lectins | Llp-1 in L. rhamnosus GR-1 | 190 | ||
| Nutrients | General better adaptation | |||
| Environment | General better adaptation | |||
| Production of molecules | Acids | Lactic acid | General in LAB | 197, 200–202 |
| Proteins | Bacteriocins | Lactacin in L. acidophilus, plantacin in L. plantarum, nisin in L. lactis | 209, 210, 212 | |
| Others | H2O2 | In many LAB | 216 | |
| Quorum-sensing interaction | AI-2 in many LAB | 219 (for L. rhamnosus GG) | ||
| Stimulation of epithelial cells | Mucins | Unknown | L. rhamnosus GG | 197 |
| Antimicrobial peptides (defensins, lysozymes, cathelicidins, etc.) | Muramyl dipeptide motif | M-tri-Lys in L. salivarius | 240 | |
| Enhancement of epithelial barrier | Upregulation of tight junctions | Secreted soluble proteins | Msp1/p75 and Msp2/p40 in L. rhamnosus GG | 231 |
| Unknown | L. plantarum WCFS1 | 230 | ||
| Barrier repair | Secreted soluble proteins | Msp1/p75 and Msp2/p40 in L. rhamnosus GG | 232, 233 | |
| Modulation of immune system (via APCs, modulation of cytokines, increased B cells, antibody production) | MAMPs | Surface layer-associated proteins (SLAPs) | SlpA in L. acidophilus NCFM | 248 |
| Pili | SpaCBA pili in L. rhamnosus GG | 254, 255 | ||
| EPS | L. casei Shirota, L. plantarum | 261, 262 | ||
| LTA | In several LAB | 257–260 | ||
| CpG-rich DNA | In several LAB | 263 | ||
| Secreted effector molecules | Proteases | PrtP protease or lactocepin in L. paracasei | 264 | |
| Short-chain fatty acids (SCFAs) | In several LAB (direct or indirect through cross-feeding) | 266–269 | ||