Explanations
In the safety page, we have seriously considered Lab safety, Biobrick safety, Project Related Material Safety, and Experimental Safety. For better application, we made our device. ( see: safety) Considering its possible social impacts, we made the safety tree for further discussion.
In the consequence tree, we consider that Avermectin has been successfully overexpressed by Streptomyces avermitilis and Toxins manufactured in E.coli have been successfully capsulated in CNC, and thus can be digested by termites fatally. Another vital certain assumption is that all bacteria are killed through suicide design. Then we imagine what TERMITE TERMINATOR may become and where it may go after their action in termites' guts. Additionally, we consider possible consequence of the device application. In sum, the safety tree discusses possible impacts from mainly four aspects: safety of streptomyces avermitilis; safety of toxins E.Coli; safety of CNC carrier and safety of Device.
- -Streptomyces avermitilis should be safe to be used in environment because if it is eaten, it's either absorbed by termites (which is exactly the consequence we'd love to see) or passed out with termites' faeces to be remained. If it is remained in the environment, it might be eaten by other organisms, which should either be mega fauna (animals of big sizes) or micro fauna (animals of small sizes). When eaten by mega fauna, tiny traces of streptomycin avermitilis are not harmful; when eaten by micro fauna, it cannot be digested before CNC resolves and the degradation period of CNC is far longer than that of avermectin. It's also safe if it remained uneaten when later it resolves or it still remains in our delicately designed device.
- -Meanwhile, the toxins E.coli is safe because its degradation period is shorter than that of CNC.
- -The CNC carrier doesn't cause any problem about safety because it's a kind of lignocellulose which is easy to degrade after a certain period. Its raw material comes from waste wood which is eco-friendly.
- -Our device also contributes to the safety of our project. When it is put indoors, it may be
influenced by mega fauna or micro fauna. Mega fauna wouldn't cause any trouble because the device is fixed and the entrance is too small for them to go in. As for micro fauna, even if they get into the device, safety is still not a problem (see Paragraph Two).
How to improve the safety of Termite Terminator?
- We choose Avermectins:
- -Can be decomposed easily by microorganism in soil
- -Sensitive to sunlight
- -High selectivity: only have effects on a few certain pests including termites and cotton aphid
- -Completely safe to large mammals under recommended concentrations
- -Completely safe to users under recommended concentration
- -Already existed mature industrial production system
- -Already have more than 3000 registered avermetin-related products in China, passing the security check of AQSIQ (State General Administration of the People's Republic of China for Quality Supervision and Inspection and Quarantine)
- An Inducible Promoter
- A Kill Switch
- A device
- An Instruction Mannual
- Environmental Safety
- Application Safety
In our plan, we shall build four constructs to express toxin proteins that helps killing termites. In case that our bacteria get outside and leak the toxic protein into the environment, we use an inducible promoter in our constructs. Only when there is arabinose in the medium, can the promoter work as usual. There is no arabinose outside the lab, so our bacterium won't leak the toxic protein.
With regard to this CidA-LrgA system and the BNU iGEM 2014 kill switch design, we designed our own kill switch as the figure shows. When cultured with our IPTG-added medium, these bacteria would live as usual to function as a mini-factory to amplify plasmids or to produce plasmids for our use, whereas they would die due to the cell membrane lysis and release of genomic DNA. Moreover, we put the lrgA gene under the control of a weak and constitutive promoter J23116 to in case of the leaky expression of the CidA to prevent cell lysis.
Our device also contributes to the safety of our project. When it is put indoors, it may be influenced by mega fauna or micro fauna. Mega fauna wouldn't cause any trouble because the device is fixed and the entrance is too small for them to go in. As for micro fauna, even if they get into the device, safety is still not a problem (see Paragraph Two).
By writing application scenarios, we have already visualized the intended impact of Termite Terminator and present Techno-moral vignettes (see: Synenergene), focusing on the potential wider impacts of our application. According to these unintended scenes, to reduce future risks, a series of warnings have been added to the Instruction Manual can be proposed (see: Instruction Manual).
