Quorum sensing is a process where cells communicate through the production and detection of autoinducer molecules. These chemical signals orchestrate and synchronize bacterial activities, as they allow information to be relayed throughout cell networks. As a result, prokaryote cell communities are comparable to a multi-cellular organism.

Quorum sensing is extremely imperative to the cooperative behaviour of cells as it allows individual bacteria to alter their activities depending on the population density of the community.

“Bacteria detect the accumulation of a minimal threshold stimulatory concentration of these autoinducers and alter gene expression, and therefore behaviour, in response.”(Waters and Bassler, 2005)

John Conway’s Game of Life, a popular representation of cellular automata, can be modelled as a demonstration of quorum sensing.  The game involves a network of cells whose ‘on/off’ status is dependent on the state of their neighbouring cells. As a zero player game, the system proceeds without further input once initiated. This model can be translated into a biological system by designing prokaryotic cells that fluoresce in response to a threshold level of an autoinducer. Addition of the chemical IPTG to designated cells initiates the system and will cause the production of autoinducer molecules. When left to its own devices, the cell network will produce a variety of patterns, showing which cells are currently emitting fluorescent light.

The Game of Life system is an illustration of the quorum sensing process but a second model can show a practical application of quorum sensing, demonstrating how it can induce negative, positive or neutral behaviour in a cellular community.
Rock-Paper-Scissors has been used as a metaphor to portray 3 rival cells that compete for survival. Each bacterium produces an auto-inducer that only affects the behaviour of one opponent cell, hence showing the specificity of quorum sensing.

Cell-to-cell interactions are not completely understood, especially within complex cellular ecosystems such as biofilms; therefore it is our aim to exploit the quorum sensing process to engineer specific interactions between bacterial species. We aim to generate complex spatio-temporal patterns to visualise the effects of quorum sensing and to track the cell interactions within the community. Also, selective patterning of the different 'species' will allow for new 'racetrack' or 'playing field' type of interactivity.

WATERS, C. M. & BASSLER, B. L. (2005) Quorum sensing: cell-to-cell communication in bacteria. Annu Rev Cell Dev Biol, 21, 319-46.