Team:CIDEB-UANL Mexico/project abstract

iGEM CIDEB 2014’s project consists on a biological filter in which sodium ions are taken out of saltwater. To achieve this objective, the project reunited 4 different genes, each one giving E. coli a certain ability to perform a specific task.

This year’s project consists of two devices: the first and main one is in charge of the removal of sodium ions. This device uses an aroma to report its effectivity. The second one is responsible of giving resistance to the bacteria to outstand conditions that would normally kill it, and also giving E.coli the ability to bind to silica or glass surfaces.

Even though the project was originally composed by this two devices, for experimental purposes it was divided into four different modules. These modules are named after their function, and the name of the project “E.CARU” is an acronym of each one of them.

The Capture module uses a completely new gene in iGEM that encodes for a protein that introduces sodium ions into the bacteria. The Aroma module is in charge of producing a mint-like odor in order to report the functionality of the Capture module. The Resistance module allows E. coli to withstand the salinity of the environment in which it is required to work, and finally, the Union module causes the bacteria to join to silica or glass surfaces, giving it the ability to act as a biofilter.

Water has been always known as a source of life, but nowadays there is not enough usable fresh water available in the world. The lack of fresh water around the world is an issue that presents a dangerous problem to our future. Only a small portion of Earth’s water is actually usable. Ninety-seven percent of the world's water is too salty for consumption or agricultural use. Furthermore, much of the fresh water is held in ice caps or other unattainable sources. This leaves approximately one percent of the global water as liquid and fresh; ninety-eight percent of which is groundwater (Bouwer, 2002). Different methods have been developed to solve these problems. One of them is desalination; converting sea water (rich in salts) into usable water, but this method is very expensive due to the great use of electrical energy, and the extraction process produces dangerous wastes to the environment (Cotruvo, 2010).

For this reason, the project is focused on developing a biological machine capable of performing desalination, reducing costs and avoiding dangerous wastes during the process. For making this possible, E. coli needed to capture Na⁺ ions in saline environments and to be removed from the water after performing its task.

Before E. coli could be able to remove Na⁺ ions from water, it needed to aquire a resistance to adverse conditions, in particular excess salt. This could be possible through a protein called “IrrE”, which makes E. coli resistant to saline environments as well as UV rays and temperature changes.
The protein NhaS (a new part), was used to give E. coli the ability to bind and capture Na⁺ ions. Also, the optimized version of the reporter “BSMT1”, a protein able to react with salicylic acid and release a Wintergreen odor, was used to know if nhaS was expressed.
The final task that E. coli should perform was to bind its membrane to silica pearls, in order to be able to be removed from the water after taking out Na⁺ ions. In order to do this, a fusion protein named L2+AIDA was used. L2 gives E. coli the ability to bind silica, and AIDA acts as a tag for making L2 a membrane protein. With this ability E. coli could be removed from water through a bio-filter, made up of silica.
The complete circuit is shown in figure 1. BSMT1 opt acts as a reporter for nhaS which is regulated by UV (to have a control over the NhaS expression), and IrrE with L2+AIDA are continuously produced.

But we realized E. coli could have a genetic overload because the circuit was too big (approximately 5000 bp). Also the time we had to finish it was not enough, as well as most of the proteins we wanted to produce were putative or untested. So for a better understanding and for determine if each piece works we divided the project into four modules: capture, union, aroma and resistance, but the project is the result of their correlation. In fact our E. coli was named E. CARU (each letter by each module).

Escherichia coli Capture Aroma Resistance Union

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Bibliography/References