Team:Paris Bettencourt/Sustainability/Fitness Cost

The ability to engineer self-replicative organisms makes it possible to reach a new level of sustainability, where the target population becomes independant. However, when going from a concept to reality, from labs lead by specialists to the community, a lot of technical challenges arise. When inventing new biotechnological devices, biologists have access to biosafety cabinets, powerful freezers and autoclaves, but the people who need our product the most won't have these. For a biological product to leave the benches and actually reach the population, it's essential to foresee its life in the hands of the people who will cultivate it and make sure it stays alive all along. Here, we provide strategies to create an durable, usable product.

When the distributed product is not the one intended

On paper, the plan is simple: volunteers grow the micro-organism, distribute it to the rest of the town and save a little fraction to start a new culture with. This could in principle last forever, but in reality the universal rules of biology soon kick back in.

Let's consider the following scenario: a wild type organism sneaks into the incubator and starts to replicate along with the engineered organism. This contaminant has been selected precisely for its ability to sneak into environments and replicate, during hundreds of years, while our organism has the burden of producing tons of enzymes to make the precious vitamins. Only the fittest survives, and we simply can't compete. After a couple of growth cycle, the worst seems unavoidable: the micro-organism that will be distributed will not be the right one. Not only this one doesn't produce nutrients, but it might not ferment the rice well or even be pathogenic.

To prevent this from happening, we identified three critical points that we have to master: - Can a contamination occur in the fermenter? - Will this contamination grow faster than the modified micro-organism? - Can the replacement go unidentified and gets distributed?

A barrier against contaminants

Completely mastering the first critical point is not an easy task for hacklabs in the south of India. If we can't afford a biosafety cabinet, we can at least take the maximum precautions so the contaminations are as rare as possible.

Reducing the burden

Mastering the second critical point equals to improve the fitness of the micro-organism on the medium, or -more likely- to make it so our modifications come with a minimal fitness cost. Modified micro-organism usually have more work to do than their wild-type counterparts: they have more proteins to produce, and more DNA to replicate. Additionally, unnatural proteins can have toxic effects when their production rate is high. It is therefore expected that our deeply repurposed bacterium or yeast would grow slower or would be less resistant to stress and growth condition changes than the natural micro-organisms.

To face this challenge we came up with an original strategy that relies on two ideas.

The Mother Cell

The cells that are grown are almost identical to the wild-type. We are now fighting from equal to equal.

Keeping control

Quality control the perfect reporter fluorescence