Background

To ensure that our bacteria do no harm to both people and environment, we need to put a set of kill-switch system into the bacteria, so that we can control the growth of them by changing the contents of culture medium.

In our project, we trigger the kill switch of E.coli by adding IPTG into the culture. IPTG can induce the expression of gene coding Limulus anti-LPS factor (LALF) downstream the lactose operator, so that the growth of E.coli will be inhibited.

Principle

Limulus anti-LPS factor (LALF) binds LPS on anti-gram negative bacterial surface tightly, forming a biofilm. This can prevent nutrient from entering the cell, causing the growth inhibition. Also, the biofilm can prevent plasmid spreading to the environment and gene pollution.

Besides, to make LALF cross the cell membrane and bind to LPS, we still need an efficient protein export signal sequence of E. coli to lead LALF into extracelluar environment.