Artificially Constructed Quorum-Sensing Circuits Are Used for Subtle Control of Bacterial Population Density
Figure 1
Essential components and mechanism of an artificial quorum-sensing circuit.
Note: the subscript “x” in RBSx represents 0.07, 0.3, 0.6, or 1.0. (A) The essential components of an artificial quorum-sensing circuit are PlacO-1-RBS1.0-luxI- TT-PlacO-1-RBS1.0-luxR-TT-lux pR-RBSx-lacZα-ccdB-TT. (B–D) The mechanism of an artificial quorum-sensing circuit is the following: (B) When IPTG is added to a culture, the promoter Placo-1 will trigger luxI and luxR expression, producing synthase LuxI (which produces the signaling molecule AHL) and an intracellular regulatory protein, LuxR, respectively. (C) AHLs will accumulate within and outside cells, and at or above a certain threshold, AHLs will effectively bind to LuxR. The LuxR:AHL complex will subsequently bind to the promoter lux pR and induce downstream expression of the lethal gene, ccdB, to produce killer protein CcdB. (D) Because more and more killer protein CcdB accumulates in the environment to kill large numbers of cells, the cell population density will decrease.