Paris Bettencourt

Biosensors are a common theme in iGEM and synthetic biology. In the six years of iGEM there have been XXX biosensors most of which are XXX sensors. However there are not many DNA biosensors in the registry. This year team Calgary developed a pathogenic E. coli biosensor and Paris Bettencourt is developing a M. tuberculosis sensor. Both the teams are using relatively new technology to create these sensors, namely, Transcription Activator Like Effector (TALE) and Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR).

TALEs are modular in nature and they contain domains called repeat variable domains (RVD) which are 34 amino acid repeats with and amino acid number 12 and 13 are variable which determines which nucleotide the TALE binds to. The specificity of these amino acids have been solved and therefore making custom TALEs targeting any sequence is very easy. CRISPRS are small extrachromosomal DNA that binds to DNA recognition protein called Cas9. The CRISPR/Cas9 complex target a sequence called protospacer which can be any sequence starting with NGG.

One of the binding elements of both these projects is the modular nature of both the TALEs and CRISPRs. These elements can be customized to detect any DNA of interest we desire. Therefore, we can use both of these systems to detect pathogenic E. coli or M. tuberculosis and any other oligonucleotide sequence we desire. However, the striking differences between the systems are how the teams are using these systems. Calgary is developing an in vitro biosensor that can be used by people in the field and Paris-Bettencourt is developing an in vivo biosensor that is used as a diagnostic tool in a laboratory environment.

This collaboration started when Paris and Calgary met at SB 6.0 in Imperial College London. We quickly figured out that both the teams are investigating platform technologies that are new and using these as a sensor. We asked the question whether our sensors are unique? This gave us the idea of the Biosensor Database [LINK].

To begin our collaboration both the teams reviewed biosensors that are already in the registry and has been part of iGEM thus far. Both the teams had video conferences weekly to think about basic questions regarding our project such as:

What is a biosensor? After an extensive literature review we settled on the definition being a biological or biologically derived system which contains a sensor element (DNA, RNA and protein) and a reporter element (visual, pH, colour, gene expression).

What are the elements of a biosensor? A biosensor can contain in vitro sensory elements such as TALEs, isolated transcription factors, repressors and/or they could contain in vivo sensory elements such as promoters, riboswitches and aptamers. In addition to the sensory element the biosensor must have a reporter element such as change in colour, florescence and gene expression.

What are some of the biosensors that are already in the registry? Some of the most common types of biosensors found in the registry thus far are chemical biosensors, followed by abiotic biosensors. However there is are only 6 nucleic acid biosensors in the registry thus far.