Modeling
Modeling Introduction
Our modeling can be divided into four parts. Firstly, in order to enable our project to be applied in real life, we designed a device placed in soil, which can attract and kill nematodes by modified engineering bacteria inside the device. Secondly, assuming there is a farmland, we took advantage of gas diffusion model and nematodes’ movement analogue simulation to find the best position where the device should be placed. Thirdly, we established a database to enlarge the range of our application, using it and our method to kill more different pests. We would appreciate that the new synthetic biological and environment-friendly method can be shared and improved with the science researchers all over the world.
Design
Device 1.0
In order to enable our project to be applied in real environment, we designed and made an entitative device, which we called device 1.0. On one hand, the production of attracting substance produced by E.coli, which attracts nematodes is low. On the other hand, the price of attracting substance is high. It was demonstrated that carbon dioxide has a function of attracting nematodes. Therefore, we choose CO2 as a low-cost assistant attracting substance.
Our device has four areas. The first area is carbon dioxide generating area. We produce CO2 by adopting limestone and diluted hydrochloric acid method, which is widely used in industry. The second area is E.coli culturing area. It includes a medium inside the device - to culture modified engineering bacteria. The third area is light controlling area, which includes a LED light. After turning on it, red emission will activate the promoter and bacterial cells will express attracting substance; turning off it, toxalbumin. The forth area is made up of a cuboid outer shell, which can support our device.
The figure above shows our real product – Device 1.0. Meanwhile, we did an experiment to show the usage of our device in lab condition.
There are mainly nine steps to apply our device in farmland just as they are showed in the video above:
Step 1. We gathered a box of soil in our farmland.
Step 2. We added culture medium onto slide glasses. Unfortunately, because of the limitation of our wet lab condition, we didn’t apply real engineering bacteria this time.
Step 3. We gathered several small stones used as CaCO3 and put them into the test tube.
Step 4. We added HCl into the separating funnel.
Step 5. We opened the faucet of the separating funnel in order to let HCl flow into the test tube under the atmospheric pressure. Then small stones reacted with HCl and produced CO2. We also showed the usage of the red LED light in the video.
Step 6. Put safety into consideration, we did our simulation in the fume hood.
Step 7. We put the device into the soil.
Step 8. After 3 hours’ experiment, we took out the device then take down the slide glasses.
Step 9. Finally, we tested the results by using microscope. And in the video, we showed the movement of a nematode that we separated from soil in Hebei Province in China.
Device 2.0
After our device has been improved, we want to figure out that how we can put our device into practice in the farmland, especially that whether or not our device would be more sufficient and economical than the killing nematodes methods used at present (crop-dusting mostly). In order to answer those questions, we need to do an analogue simulation of the movement of nematodes to determine the most suitable place in the farmland to put our device. Our modeling process is as follows:
Firstly, we suppose that modified engineering bacteria can produce ideal concentration of attracting substance and toxic protein (the ideal concentration is in reasonable range). Then, because E.coli can only grow on the surface of the medium and considering the problem of space utilization percentage, we changed the medium’s shape to sphericity to obtain the highest space utilization percentage. Meanwhile, our device has been shaped to sphericity too, and the LED light has been moved to the center so the whole surface of medium can get the same radiation. Moreover, we choose mini LED light bulb and solar energy as the power to save cost and energy.
We also made a video to show the inner structure of device 2.0.