Overview
Quorum sensing (QS) is cell-density-dependent communication in which bacteria produce, secrete, and detect small signaling molecules (autoinducers) to coordinate group behaviors — including biofilm formation, virulence factor production, siderophore synthesis, and antibiotic resistance gene expression. When autoinducer concentration reaches a threshold (indicating sufficient "quorum"), gene expression programs switch on collectively.
Key Systems
- AHL (N-acyl homoserine lactones): Gram-negative QS signals (LuxI/LuxR system). Used by pseudomonas aeruginosa, Vibrio, Burkholderia.
- AI-2 (Autoinducer-2): Universal interspecies signal (LuxS-dependent). Enables cross-species communication within polymicrobial biofilms.
- Farnesol: C. albicans QS molecule that inhibits yeast-to-hyphal transition — but can be overridden by bacterial signals in functional shielding contexts.
WikiBiome Relevance
- Biofilm virulence: QS coordinates the transition from planktonic growth to biofilm mode, enabling functional shielding and antibiotic resistance.
- Anti-QS interventions: Quorum quenching — disrupting QS signaling — is a non-antibiotic strategy to attenuate virulence without killing bacteria (avoiding resistance selection). Ethiopian medicinal plants show anti-QS activity [1]; thymoquinone from Nigella sativa disrupts QS [2].
- NEC: QS-regulated virulence in NEC-associated pathogens [3].
- Interkingdom: Fungal-bacterial QS cross-talk modulates polymicrobial biofilm dynamics [4].
Cross-References
- biofilm — QS-regulated community structure
- functional shielding — QS coordinates interkingdom biofilm behavior
- pseudomonas aeruginosa — paradigm QS organism
- antimicrobial resistance — QS-regulated resistance gene expression