This year’s UCAS iGEM Team is trying to develop a safe, smart and efficient system to deal with antibiotic residues in nature and industrial products. Our engineered bacteria will not express degrading enzymes unless antibiotic is presented, and it kills itself after leaking into wrong places. We choose a non-pathogenic chassis, E.coli, and pay high attention to our project design, lab work, shipment, etc.
Safety project design
TA system and Kill-switch
In our system, the degradation enzyme can only be expressed under high concentration of tetracycline antibiotics. As long as antibiotics decrease to a low concentration, antitoxin expression will become less than toxin which leads to the death of our bacteria so that it won’t be an antibiotic resistant superbug after accomplishing its mission.
Since TetX can only function as degradation enzyme in aerobic environment，and its gene majorly transmits by vertical gene transfer rather than horizontal gene transfer. Besides, MnCcP cannot easily be expressed in E.coli with activity if we add enough heme. So these degradation enzymes won’t exert negative impact outside laboratory, and won’t harm any plants, animals or human beings.
In order to prevent the leak out of genetic engineering bacteria together with its degradation enzyme genes (antibiotic resistant genes), we install a filter membrane at the exit of water channels in our hardware to inhibit the escape of our bacteria, and the bacteria in activated sludge can also be pumped back bio-pool.
In our questionnaire, we asked people about security problems in our project, for instance, whether it is acceptable to use genetically modified organisms (GMOs) in waste water treatment plants (WWTPs) or hospitals to degrade antibiotics, only 11% of people found it unacceptable, with 9% strongly reject the use of any GMO outside laboratory. Most of them (72%) think it is acceptable as long as there are certain security measures. That is also why we use a biocontainment strategy and prevent bacteria escape at the same time.
Safe lab work
According to the requirements of iGEM policy we never performed any dangerous experiments in daily experiment or faced any unusual safety issues. The team members followed some basic regulations as below:
- All involved participants needed to understand the experiment and follow the safety regulation in laboratory.
- All involved participants must wear rubber gloves before conducting experiments.
- The super-clean bench was sterilized using UV-light every day before conducting experiments.
- All liquid and solid waste potentially containing living organism was sterilized.
- Most of the culture medium containing antibiotics should be inactivated by high temperature of autoclaved sterilization.
- All laboratory waste should be classified into three categories, including glass, plastic and paper before throwing into garbage cans. And all equipments with needles should be thrown into a specialized garbage can.
- The last person to leave the lab always made sure that water, electricity, gas, and the air conditioner were shut down, and doors have been locked before leaving.
The DNA parts were safely confined within submission kit as the Parts Registry requires.