Description of our project

Introduction: motivation and background

This year, our projects focus on biological methods for warning and countermeasure against water bloom and red tide. As we know, this ecological disaster, due to nutrient overload and followed by oxygen deprivation, tortured many countries and caused gigantic economic loss and ecological disruption. We propose that to prevent it happen, a precise sensor for alarming the arrival of water bloom and an effective actuator to solve it are needed. So our projects can be summarized as two parts: The first goal is to develop a synthetic system which can sense the outer signal and have a precise decision-making about to what degree will there be a water bloom. We will facilitate a fine-tuned ratio sensor sensing the ratio of nitrogen and phosphorus to achieve this.

The second goal is to construct an actuator with ‘portable’ gas vesicles which enable our engineered microbes to float on the water surface.

The third goal is to provide our actuator with several functions making it a versatile cleaner to contain the water bloom.

What trigger water bloom?

The well-recognized culprit of water bloom is overload of nutrient (eutrophication).Take the Baltic Sea as example, dumping from sewage-treatment plants, farming and industry has poured about 20 million tons of nitrogen and 2 million tons of phosphorus into the Baltic over the past 50 years, which give rise to long-lasting algal blooms. The net effect is an excess of phosphorous, which fuels nitrogen-fixing cyanobacteria and triggers algal blooms as the essential condition. Another crucial factor is an excess of nitrogen which can amplify the effect and enhance overgrowth of the cyanobacteria and alga. And many research indicate that many a particular ratio of this two element, relatively stable, coincide with the water bloom. It suggests that a ratio sensor to alarm for water bloom is reliable.

What is a ratio sensor?

As we have mentioned, a ratio sensor could be an indicator for the arrival of water bloom. But only when we make a fine-tuned ratio sensor which can sense the two different signals(nitrogen&phosphorus) precisely, account the ratio accurately and perform a remarkable reporting signal, can we assure that it is a fine-tuned and reliable alarm.
a) We will facilitate phoB promoter and NtrB promoter for sensing phosphorus and nitrogen respectively.
b) Ratio accounting is implemented with an artificial system of RNA –mediated regulation.
c) We choose GFP as the reporter to show our result.

What is gas vesicle?

To facilitate our E.coli to float on the water surface, we should equip our engineered E.coli with portable generators of gas vesicles. The gas vesicle is a hollow structure made of protein. It usually has the form of a cylindrical tube closed by conical end caps. Gas vesicles provide aquatic microbes with buoyancy so that they can control their vertical migration. It could have been a great tool to hold our engineered E.coli on the water surface, as the previous teams had shown us. However, due to the horrible length of its coding genes and the heavy burden it brought about to its host, the practical application remain difficult and uncertain. Our team determines to break through the task by fine-tuning the expression pattern of gvpA and gvpC which test the most economical way to provide buoyancy.

How can our actuator curb the water bloom?

So if the two projects above go well, we will focus on constructing a versatile warrior which can stifle the water bloom in the cradle. We may take advantage of some genetic parts to absorb and fix the nutrients , release toxins restricted to the toxic cyanobacteria and alga and even facilitate the mechanism of vertical migration thereby bring the nutrients to the deeper area.