As you’ve probably heard, several companies are working towards putting colonies on Mars. If we want humans to thrive, there we have several problems to address first. One of the most pertinent is food. If we want fresh produce on Mars, we first need to sort out the planetary dust that covers the surface, known as regolith. To grow plants safe for consumption, a toxic chemical called perchlorate has to firstly be removed.

The aim of our project is to design a bioreactor containing genetically modified E.coli that can break down perchlorate using transgenes from another bacterium (A. suillum). The main products of this reaction will be chloride (which we’ll remove) and oxygen (which astronauts can use to breathe - at least until plants produce the oxygen for them).

Whilst space exploration is promising it can also cause issues on Earth.

Ever thought about what happens to waste rocket fuel? Turns out, it can end up contaminating our drinking water. As you can imagine, this is an issue; the culprit here is once again perchlorate. Our second aim is for the bioreactor to be able to be optimised for removing this chemical from water by installing a filter. If the bioreactor were to be used outside of the lab the hope is that it can be used in water purification plants to turn perchlorate into chloride and harmless oxygen.

We are designing a bioreactor that will break perchlorate down into oxygen and chloride. We will do this by inserting genes from the bacterium Azospira Suillum into our chassis, Escherichia coli, which will synthesize perchlorate reductase and chloride dismutase.

This is an important problem because on Earth perchlorate is a contaminant in drinking water, and so our bioreactor will be include a filter to extract the compound out of water. This could also have applications on a possible Mars colony, as we could use the perchlorates found in Martian soil to produce oxygen. This is a synthetic biology problem because this reaction is volatile and doing it with chemicals would be dangerous.

What is perchlorate, and why is it a problem?
Perchlorate is a chemical with a structure consisting of one chlorine atom and four oxygen atoms arranged in tetrahedral geometry (ClO4-). This anion has been found to accumulate in groundwater because its reduction requires a very high activation energy (citation needed). Perchlorate also makes up 0.5-1% of Martian regolith (the top layer of loose soil, dust and rock). As mentioned before, perchlorate is toxic (citation needed) - this means the compound is harmful both on Earth as a water contaminant, and on Mars for any potential colonies we might form. Synthetic biology offers the best solution so far to this problem as the chemical method to reduce perchlorate is explosive and so is a further danger to human life.
What is our solution?

We will use a naturally occuring operon to produce two key enzymes: perchlorate reductase and chloride dismutase from the bacterium Azospira Suillum. Before transforming E.coli with these genes we will attempt to shorten or split up the operon and then optimize it for our chassis.

We want to split up the operon to prevent smearing, which was the largest obstacle for previous teams, and to make it easier to test if each small segment is working.

We will then optimize it for E. coli, specifically for secreting chloride dismutase using various secretion systems such as the twin-arginine translocation (TAT) pathway using signal peptides.

This will be placed into a bioreactor containing a water filtration system. Potentially the E. coli will grow on graphene within the bioreactor, as graphene is a light enough material to transport into space, and we could produce an electromagnetic field across the graphene to enhance the rate of reaction.