quorum sensing: a standalone construct

Nealson, Platt, and Hastings (1970) first described the mechanism while studying luminescent marine bacteria: they showed that the light-producing enzyme system stayed switched off in a fresh, dilute culture and turned on only once the cells accumulated to high numbers, because a small signal molecule the cells release builds up in the medium and, above a threshold, activates the genes. Fuqua, Winans, and Greenberg (1994) named this behavior quorum sensing, borrowing the town-meeting idea that a quorum, a minimum number, must be present before the group acts, and mapped the shared genetic machinery (the LuxR and LuxI protein family) that lets each cell both make the signal and respond to it. Waters and Bassler (2005) synthesized the field, documenting that many bacterial species use such signals to switch on collective activities including bioluminescence, biofilm formation, virulence, and the exchange of genetic material. What makes quorum sensing distinctive is that it explains how single-celled organisms with no nervous system behave as a coordinated population: each cell measures the local concentration of a self-produced chemical as a proxy for how many neighbors are present, and gene expression flips only when the group is large enough for a joint response to pay off.[1][2][3]

Unit

A regulatory process in which gene expression is controlled by the concentration of a self-produced signal molecule that tracks cell population density

Recovery means

Not applicable

Measured by

Identified by linking a diffusible signal molecule (such as an acyl-homoserine lactone or a peptide) to a density-dependent change in gene expression, using reporter assays, signal-molecule chemistry, and mutants of the signal-synthase and receptor genes