The principle of quorum sensing
Microorganisms can sense the presence of their own kind based on quorum sensing which is a form of chemical communication. Depending on their cell density, quorum sensing allows these cells to activate or deactivate certain gene expression cascades (Waters and Bassler, 2005) for a specific function.
Our sensor cells, Cellocks, are immobilized in agar chips. To make the chips, we mix the Cellocks with liquid LB agar. In the course of our project, we designed a casting mold specifically for the production of our agar chips. When the agar has cooled down, the chips are cut out of the mold and are ready to use. Storage of the readily usable sensor chips is possible for up to two days at 4°C when using LB medium or up to five days if TB medium is used. A detailed description of the sensor chip manufacturing can be found in our Protocols section.