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From 2014.igem.org

Biological Tools

Integrases – Molecules working as scissors on the DNA

Integrases are proteins that work like scissors on two specific sites on the DNA.

Within those two sites they can invert the sequence or they can completely remove it. The genes coding for those integrase-scissors and their corresponding specific sites can easily be inserted into bacteria.

This way you can control which genes are expressed by defining integrases present in your system.

In our project integrases working as scissors for DNA is one of the core components we tried to implement in Mosaicoli.

Quorum sensing – Communication using signal molecules

Bacteria can interact with their surroundings and neighboring cells via cell-to-cell communication. Using this communication they can coordinate the expression of genes and thus the overall behavior of the population of bacteria.

Quorum sensing describes a system including a stimulus and a response. It is the synthesis, secretion and diffusion of small molecules, which are able to trigger a response.

Already in the early 1980s by investigating a specific strain of bacteria it was found that depending on the cell density and the concentration of signal molecules, bacteria were able to communicate.
The communication was visualized by bioluminescence, which is the production and emission of light by a living organism. It was then found that the molecule inducing this bioluminescence is N-(3-oxohexanoyl)-L-homoserine lactone, which we will just call AHL here and is produced by the enzyme Luxl (Please consider the figure below for the flow of AHL between cells).

Another enzyme named LuxI produces this AHL. The AHL produced in one cell can then diffuse out of the cell and reach other cells. In those other cells it binds and activates a protein called LuxR. This LuxR protein regulates the gene transcription (first step on the way from DNA to proteins).

Further research on such signal molecules was conducted and other systems of AHLs corresponding to the LuxR/LuxI system were found. These additional systems are called LasR/LasI and RhlR/RhlI.