TABLE 1.
Microbial signaling systems
| Signal(s) | Microbe(s) | Synthesis | Precursor(s)a | Receptor(s) | Regulated function(s) | Reference |
|---|---|---|---|---|---|---|
| Acyl homoserine lactones (AHLs) | Proteobacteria | LuxI-type enzymes | SAM, acyl-ACP | LuxR-type proteins | Diverse processes | 21 |
| AinS-type enzymes | SAM, acyl-ACP, acyl-CoA | Two-component kinase | ||||
| Linear oligopeptides | Gram-positive organisms | Genetically encoded (e.g., B. subtilis) | Secreted prepeptide | Two-component systems, phosphorelays | Diverse processes | 77 |
| Cyclized oligopeptides | Gram-positive organisms | Genetically encoded (e.g., S. aureus) | Secreted post-syn mod. prepeptide | Two-component systems, phosphorelays | Virulence genes | 72 |
| γ-Butyrolactones (GBLs) | Streptomyces spp. | AfsA-type GBL synthase | Acyl-ACP, glycerol | ArpA-type repressor, GBL-binding protein | Secondary metabolism; antibiotics and sporulation | 37 |
| Furanosyl diester (+/− boron); AI-2 | Diverse taxa (no α-Proteobacteria) | LuxS AI-2 synthase | Methionine salvage (DPD) | Vibrio spp. LuxP/LuxQ/LuxO phosphorelay; unknown for other systems | Luminescence and diverse processes | 80 |
| cis-11-Methyl-2-dodecenoic acid (DSF) | Xanthomonas spp., perhaps others | RpfB, RpfF | acyl-CoA? | RpfC, RpfH | Virulence and pigmentation | 100 |
| 4-Hydroxy-2-alkyl quinolines (PQS, HAQs) | Pseudomonads | pqsABCDE, pqsH | Anthranilic acid | ? | Global regulation, virulence | 13 |
| Palmitic acid methyl esters (PAME) | Ralstonia solanacearum | PhcB | SAM (?), fatty acids | PhcR regulator | Virulence, exopolysaccharides | 18 |
| Putrescine | Proteus mirabilis | SpeA, SpeBb | Ornithine, arginine | ? | Swarming motility | 87 |
| A-signal (amino acids) | M. xanthus | AsgAB-dependent protease | Cell surface | SasS/SasR/SasN proteins | Early development, aggregation | 46 |
| C-signalc | M. xanthus | Translation product | CsgA protein | FruA, unknown HPK (csgA) | Coordinated motility, fruiting body development | 46 |
| Cyclic dipeptides | Many taxa | ? | Amino acids? | LuxR-type proteins? | Secondary metabolism | 35 |
a
DPD is 4,5-dihydroxy-2,3-pentanedione. CoA is coenzyme A.
b
Based on E. coli biosynthetic pathway.
c
C-signal is a cell surface-associated protein (17-kDa processed form of CsgA). HPK, histidine protein kinase; secreted post-syn mod. prepeptide, secreted post-synthetically modified prepeptide.