The Issue

Life-threatening pathogenic infections cause thousands of deaths every week all around the world. The effective and efficient identification of the infectious pathogens would facilitate the clinical treatment of these diseases. Nevertheless, current methods for identifying pathogen have many drawbacks, such as long period for testing, multiple complex reactions caused high cost and lack of portable facilities. The clinical diagnosis of the infectious pathogens would benefit significantly from the specific and sensitive pathogen identification methods better than existing methods such as pathogen culture, immunoassays and polymerase chain reaction (PCR) testing.

Opportunities for synthetic biology in mobile health

By the inspiration of mechanisms of quorum sensing, the classical iGEM system under reconstruction and utilization, We designed a novel pathogen detection and identification system, it is quiet convenient as the sensing system is made in the form of test paper, which can be carried at hand. More importantly, it is much more safer than the traditional iGEM detectors, as the system we use is S. cerevisiae (budding yeast) . To accomplish the detection, the suspected patients only need to add a little bit water as well as the pathogen-riched biological sample like snot and tears. The color change of the test paper indicate the infection by specific pathogen. Also, as some infections are caused by multiple pathogens, in order to detect the different pathogens at the same time, we construct a switch-box, which is composed of different sensors and different reporters. This system could increase the speed and portability of pathogen identification, decrease the cost for producing practical facilities, and enable specific identification of distinct infectious pathogens. The challenge is addressed by implementing the genetically modified S. cerevisiae (budding yeast) for testing signal molecules from pathogens, which is supposed to be effective, reliable, safe and cost-effective.

Idea of the project

The project introduces the use of genetically engineered cells in a pathogen identification system. By virtue of the switchable haploid/diploid form of yeast , we aim to construct two kinds of haploid budding yeast, one is to sense the signal molecules from pathogens , the other is to report the identification of pathogens, referred as sensing module and reporting module, respectively. By mating the sensing module and reporting module, two differently engineered yeasts, the signals from pathogens are sensed and reported by change in the color of the yeast colony. The N-Acyl Homoserine Lactone (AHL) is the signal for testing by the sensing module, which is the molecule for quorum sensing in Gram-negative bacteria with specificity for each different species of pathogens. Tetracycline-controlled transcriptional activation system (Tet-off system) is introduced to transmit signals from sensing module to reporting module. Considering the specificity and sensitivity of this pathogen identification sensor, this technology could prove useful for clinical test, medical diagnostics, water quality monitoring, and other potential applications.

Achievement

• We accomplish the communication between eukaryotic cells and parkaryotic cells in the first time via introduced the genetically modified quorum sensing system from Gram-negative bacteria (LuxR-AHL controlled transcriptional activation system) to S. cerevisiae (budding yeast) by designing eukaryotic-parkaryotic mosaic transcriptional activator and promoter, referred as LuxR-tVP16 and Plux-mCyc respectively. Which expand the possibility of iGEM projects in the future.
• We designed and completed the switching system by mating different reporting modules with the sensing module.
• We constructed mathematical modeling to demonstrate the sensitivity and robustness of this system with combination of modified quorum sensing and tetracycline controlled transcriptional activation systems.
• We introduced several safety mechanisms to this engineered biological testing machine.
• We deposited several novel BioBricks to the Registry.
• We improved the existing BioBricks.
• We introduce the project and synthetic biology to society by making videos and other activities.