Widespread algal blooms cause extensive damage in ecosystems. Compared to physical or chemical methods, biological treatment for algal bloom is less expensive and more environmentally friendly. Peking iGEM is dedicated to constructing engineered microorganisms for the elimination of cyanobacteria and recovery of ecosystems.

An antimicrobial lysozyme was introduced to kill cyanobacteria since lysozyme could disrupt the outer membrane of cyanobacteria. In addition, we equipped our transgenic cells with features that allow for buoyancy and attachment, making our project more efficient. During this process, an enzyme is also secreted to degrade a deleterious product of cyanobacteria. After eradicating the cyanobacteria, our engineered bacteria will commit suicide, and the ecosystem is finally restored.

This project is an innovative treatment for water bloom, and has potential applications in the field of ecosystem remediation.

Demo2 first
Peking iGEM: Lab
Demo2 first
Peking iGEM: The Killing effects
Peking iGEM: Peking iGEM Club
Peking iGEM: Fluorescence Picture

Killing the cyanobacteria is the directly efficient way to reduce an algal bloom. Lysozyme was introduced to annihilate cyanobacteria. The lysozyme could deconstruct the outer membrane of cyanobacteria and further lyse the cyanobacteria. Lysozyme immune system was implemented to protect our genetically engineered E. coli. Our goal is secreting lysozyme to kill cyanobacteria without harming our E. coli.

Killing Improvements:
A lectin of the cyanobacteria was expressed on the surface of our E. coli cells so that E. coli can bind to the cyanobacteria. Our experimental results show that E. coli cells do bind to the cyanobacteria, indicating that the killing efficiency of our project is greatly enhanced according our computational models. We also equipped our E. coli with gas vesicles so that our project can be feasible in the real ecosystems.

This year, Peking iGEM aimed at treating the problem of algal bloom with synthetic biological tools. Genetically engineered E. coli was implemented to both reduce the algal biomass and degrade the toxin.

Degradation :
Microcystis aeruginosa is the most common cyanobacteria during an algal bloom, which can secrete a deadly toxin microcystin. To decrease the negative effects of the toxin on water ecosystems, we introduced an engineered bacteria that can secrete a microcystinase-MlrA protein to hydrolyze the toxin.

Suicide :
After killing cyanobacteria and degrading toxin, the remaining bacteria should be eliminated or they would potentially cause negative effects to the environment. We constructed the suicide system using lysing system from phage, since E. coli should be controlled to commit suicide after accomplishing their mission.

Modeling :
Our modeling focused on supporting the whole project. We used Monte Carlo simulation to analyze the enhancement of binding of E. coli to cyanobacteria to the efficiency of killing. Another model about cellular burden was built to find optimal expressing efficiency. Furthermore, a macroscopic simulation that predicts the real situation would provide insight for the whole project.

Human Practice :
Investigation lies much beyond lab bench. Great insight would be discovered by in field study. We visited Taihu Lake, one of the biggest lake in China suffering algal bloom. We interviewed the researchers and acquired knowledge about cyanobacteria in lake ecosystem. Besides, we were dedicated to communicating with other teams. We also established iGEM Club in Peking University to popularize iGEM competition.