Team:Bielefeld-Germany/Biosafety/Biosafety System L

From 2013.igem.org

Safety system L (leaky)

The lac repressor/operator system uses E.coli to regulate the production of enzymes and because of this E. coli also regulate its metabolic stress. Enzymes only are produced when they are required. LacI is a repressor which is able to inhibit the lac operon in the absence of lactose by binding to the DNA at the lac operator site called lacO. Because of this repressor DNA polymerase is inhibited so it can’t read the sequences behind the operator lacZ (β-galactosidase), lacY (lactose permease) and lacA (thiogalactosidase transacetylase) which are responsible for transporting and metabolism of lactose in E. coli can’t be transcribed. The structure of the lac operon is shown in the image below.

Structure of lactose operon and regulatory units.

System L in the MFC: In this case the mikroorganism is in the MFC with sufficient L-rhamnose. It comes to an expression of lacI which blocks the lac-promoter by binding and alr which switches L-alanine to D-alanine. Because of the fact that lacI blocks the lac-promoter the RNase Ba can't expressed.

System L outside of the MFC: In this case the mikroorganism could get out of the MFC by damage or incorrect handling. Outside of the MFC there isn't enough L-rhamnose. So... E.coli dies.

References:

Agnes Ullmann (2001): Escherichia coli Lactose Operon. In: Encyclopedia of Life Sciences