Human Practices

It is undeniable that mosquitoes have the potential to pose significant public health threats as disease vectors, in addition to simply being annoying to most people. Perhaps as a testament of the power of annoyance in driving innovation, people have come up with astonishingly diverse ways to repel, trap, or kill mosquitoes. Why then, one may ask, is our team working on yet another mosquito trap? In addition to the practical improvements given by our trap such as ‘always-on’ operation and avoidance of toxic sprays, part of what drew us to the concept in the first place was a sense of philosophical beauty.

The E.coli-based mosquito trap we are developing is meant to be self-sustaining in that the exoskeletons of trapped and killed mosquitoes are digested to provide nutrients to the bacteria responsible for synthesizing and secreting the chemical attractants. In theory, the higher the mosquito population density, the more abundant the nutrient source for the cells, which would promote more rapid growth and secretion of attractants to further increase trap effectiveness. From an engineering perspective (engineers are especially well-represented in our team), such a system may be described as adaptive. We think it is a more elegant solution compared to non-adaptive systems like most conventional traps or insecticides.

When we first set out on this project, it was clear to us that approaching the seemingly mundane problem of mosquitoes with a solution based on synthetic biology and ‘genetically engineered’ organisms would almost definitely not result in a solution that could plausibly be implemented in the near future as public acceptance of synthetic biology and genetic engineering remains low. Rather, our intention was to contribute to the long-term development of synthetic biology from a science into a technology by striving for a proof-of-concept that it can indeed produce viable solutions to existing problems, and also assisting in the establishment of a standardized part library.

In the design of our prototype trap, thought was given to the initial motivation for a bacteria-based mosquito trap. We were particularly interested in the self-sustaining feature of the design which, in theory, would allow traps to be constructed and operated with only some sort of growth medium and mosquitoes as inputs. In addition, the use of bacteria as carriers for the active (attracting and digesting) elements of the trap, it would be possible for new traps to be propagated from existing traps by simply inoculating fresh culture medium with bacteria from the progenitor device. This opens up the possibility of rapid and low-cost deployment in regions without access to the technology and manufacturing facilities to build conventional mosquito traps. In keeping with this vein, we decided to construct the body of our prototype by re-purposing PET beverage bottles. The decision was taken to demonstrate that the basic version of the trap can be built using low or no-cost materials (this minimal cost version would not include the electrical component to immediately kill trapped mosquitoes but rather rely on trapping them and effecting eventual death through starvation).

As we worked through the project and thought about the eventual validation of our design, we reviewed the safety information provided by iGEM and consulted with our instructors. An ideal validation study of our final trap prototype would be to deploy it in an area populated by mosquitoes and compare its effectiveness in trapping and killing mosquitoes to a control device without the engineered E. coli. However, we quickly recognized the unacceptable risks associated with deploying a novel genetically engineered bacterial strain into the environment, not to mention the lab biosafety rules explicitly prohibiting such release of live cells. Therefore, we decided to proceed with a limited validation using laboratory assays for our intended gene products including L-lactic acid, indole, and chitinase.