The Search for the Evolution of Biological Cooperation through a Synthetic Yeast System

Cooperation is widespread in nature: it can be seen in many biological settings from the macromolecule level to the organismal level. How might a cooperative system evolve from inception? To study this, I have used CoSMO (Cooperation that is Synthetic and Mutually Obligatory), a yeast-based system amenable to quantitative and genetic analyses. CoSMO consists of two non-mating yeast strains, each engineered to provide essential metabolites to the other strain, while being metabolically dependent on the other. Evolved CoSMO cocultures exhibit an improvement in viability, shown by their ability to grow at significantly lower starting cell densities compared to their ancestors. To identify pro-cooperative changes that lead to viability increase, I will revive evolved CoSMOs from frozen stock at different time points along its evolution. I will then isolate clones from each cooperator strain and assess their contributions to improved viability by reconstituting them into new CoSMOs with their ancestral partner. If an evolved clone indeed contributed to improved viability, its growth, death, and metabolite consumption and release properties will be measured.  By doing the same analyses on independently evolved CoSMO lines, we can obtain insights about the diversity in evolutionary trajectories of cooperative systems. By understanding how cooperative systems have evolved, and how these systems affect the individual cooperators over time, we can better comprehend and apply the idea of “working together” to benefit areas in medicine, ecology, and agriculture.