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Team:StanfordBrownSpelman/Human Practices
From 2014.igem.org
Uses of UAVs & Orthogonal
Systems in Nature
Systems in Nature
Images ● EPA Partnership ● Scientific Expert Interviews (rename?) ● Publications ● References
Many of us are aware of the immense potential of synthetic biology. Yet, like any other tool, it can be used both benevolently and malevolently. This year, our team worked on the creation of a biosynthetic and biodegradable UAV, or Unmanned Aerial Vehicle. In the present day, UAVs are used for a wide range of purposes, but many people are only familiar with their use in the military. The goal of our human practices project this year was to propagate knowledge about the non-military and humanitarian uses of UAVs. In the process, we interviewed a wide variety of people- experts on UAVs, scientists, businesspeople, and civilians at large. The information gleaned from these interviews was integrated in to an article about modern uses of UAVs. This article was published in online and print media. A few videos from the interviews we conducted can be seen below.
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Our Work with the EPA: Synthetic biology in the air: Biological UAVs and environmental safety concerns
We are currently working on a series of projects towards the construction of a fully biological unmanned aerial vehicle (UAV) for use in scientific and humanitarian missions. The prospect of a biologically-produced UAV presents numerous advantages over the current manufacturing paradigm. First, a foundational architecture built by cells allows for construction or repair in locations where it would be difficult to bring traditional tools of production. Second, a major limitation of current research with UAVs is the size and high power consumption of analytical instruments, which require bulky electrical components and large fuselages to support their weight. By moving these functions into cells with biosensing capabilities – for example, a series of cells engineered to report GFP, green fluorescent protein, when conditions exceed a certain threshold concentration of a compound of interest, enabling their detection post-flight – these problems of scale can be avoided.
However, housing live cells on an aerial system presents a new set of problems, chief amongst which is the concern of horizontal gene transfer. Bacterial cells can perform conjugation, a process which allows for plasmids (small, circular strands of DNA) to be copied from one organism to another. In our case, we must take steps to protect the environment from our cells and avoid the possibility that our engineered genes proliferate throughout ecosystems. In addition, not dissimilar to the problem of mechanical UAVs getting lost or crashing and leaching toxins into the environment, we must address what might happen if our biological UAV were to crash and allow the cells on its biofilm to act as an invasive species.
We are harnessing the power of genetic engineering to mitigate both of these scenarios. To address horizontal gene transfer, we are recoding the cells on our UAV to use the UAG stop codon, which usually signals the truncation of a protein during translation, as leucine, an amino acid, instead. When we engineer the genes we wish to transform into our cells (an “amberless” strain, as UAG stop is called “amber”), all instances of UAG will be replaced with different stop codons, and all leucine residues will be coded for by UAG. Thus, any engineered genes which are passed from an amberless cell to a normal cell in the environment will not be read correctly, as each leucine residue will be instead be interpreted as “stop” and will result in the production of a non-functional protein fragment. We hope that our amberless strain can be adopted as a model for any engineered organisms one might wish to send into the environment. Finally, to address the invasion of our cells into the environment, we are engineering a pressure-sensitive “kill switch.” Upon crash, the cells will activate quorum sensing (a method of intercellular communication), which will act as a signal to begin producing a set of proteins which can degrade the cellulose acetate base material. The UAV itself will degrade into glucose, which can be taken up by organisms in the crash environment, while the engineered cells will be killed by the free acetate, which, hopefully, will be in high enough concentration to harm the biofilm but not the crash environment.
