Before we get started:

Although there are a plethora of oral bacteria, only a handful cause tooth decay, and chief among those is S. mutans (see [Project Overview] for more information). For our modified E. coli to deal with this threat, we need to find a way for them to get close to S. mutans colonies in the oral environment.

Competence Stimulating Peptide, or CSP, is an important quorum sensing (QS) pheromone specific to S. mutans, playing a huge role in their genetic response to population density. The system works since S. mutans continuously release CSP, which bind to the surface receptors of other S. mutans nearby. Check out [Control: Target] for more information on CSP.

The exclusivity of CSP and the ubiquity of its receptors in S. mutans makes it a great candidate for creating an anchoring module!

So how did we do it?

Because of size constraints, we did not want to use the actual CSP molecule itself. Instead, we found C16, a functionally active fragment of CSP which still binds to CSP receptors. Compared to CSP, C16 is smaller and more suitable for attachment on the E. coli surface.

Now that the attachment candidate is found, what’s left is to express it on the surface of E. coli, so it can interact with S. mutans.

For that purpose, we found INPNC, a surface display protein in E. coli biobricked by the 2011 Edinburgh iGEM team. Using INPNC as basis, we created the INPNC-C16 fusion protein, which displays C16 on the surface of E. coli to achieve the results we want.

At last, our circuit is complete!

Putting it to the test!

Our result

Reference

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