Quorum Sensing
QSAlso known as: autoinduction, cell-density signaling
A cell-cell communication mechanism where bacteria produce and detect diffusible signaling molecules, enabling population-density-dependent coordination of gene expression.
Quorum sensing is a bacterial communication system in which cells synthesize, secrete, and detect small signaling molecules called autoinducers, enabling coordinated gene expression responses that depend on population density 1.
How It Works
In the canonical LuxI/LuxR system from Vibrio fischeri, the LuxI synthase produces acyl-homoserine lactone (AHL), which diffuses freely across cell membranes. At low cell density, AHL concentration remains below the detection threshold. As the population grows, AHL accumulates in the extracellular environment. When it exceeds a critical concentration, AHL binds the LuxR transcription factor, activating expression of target genes including bioluminescence operons.
Synthetic biologists have repurposed quorum-sensing components as programmable cell-cell communication channels. The LuxI/LuxR and LasI/LasR systems from different bacterial species use distinct AHL molecules, providing orthogonal communication channels for multicellular circuits. These have been used to build synchronized oscillators, population-level logic gates, and pattern-forming systems 2.
You et al. demonstrated one of the first synthetic quorum-sensing applications by coupling AHL production to expression of a killer gene, creating a population control circuit that maintained cell density at a programmed setpoint 2. This established quorum sensing as a fundamental building block for engineering multicellular behaviors.
Computational Considerations
Modeling quorum sensing requires coupling intracellular gene expression dynamics with extracellular signal diffusion. ODE models describe well-mixed populations, while partial differential equation or agent-based models capture spatial effects such as signal gradients in biofilms or microfluidic devices. Parameter estimation from bulk and single-cell fluorescence data calibrates AHL production rates, diffusion coefficients, and LuxR activation thresholds 1.
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ODE and agent-based models simulate quorum-sensing dynamics across spatially structured populations. Parameter estimation from bulk fluorescence data calibrates signal production and detection thresholds for synthetic QS circuits.