Analysis of Genomic Sequences and Evolutionary Diversity in a Synthetic Cooperative Yeast System

Cooperation is a widespread phenomenon observed between molecules, cells, individuals, and communities. In such systems, both cooperators benefit from the altruistic act. How have cooperative systems evolved from an incipient state? To address this, we utilized CoSMO (Cooperation that is Synthetic and Mutually Obligatory), an engineered system that models incipient cooperation. CoSMO consists of two non-mating yeast strains that cooperate via metabolite exchange.  Evolved CoSMO cocultures exhibit improved viability, defined as their ability to grow from significantly lower starting cell densities compared to their ancestors. Phenotypic changes in evolved cooperators that contribute to improvement in viability have been identified, such as increased metabolite release and increased starvation tolerance. We will identify the molecular basis of these phenotypic adaptations by performing genome-wide re-sequencing on evolved cooperators. Specifically, we will extract genomic DNA from evolved cooperators at early and late stages during their evolution. We will then compare the genomic sequences of the evolved types to their ancestors in order to identify relevant mutations responsible for the observed phenotypic changes. We will perform similar analysis on replicate lines to quantify the diversity in evolutionary trajectories of incipient cooperative systems. If specific mutations that alter cooperator phenotype are observed, this suggests a deterministic mechanism to stabilize CoSMO. If assorted mutations contributing to the phenotypic changes are found, diverse mechanisms to stabilize CoSMO is implied. In both cases, identifying the molecular basis of pro-cooperative changes in evolved CoSMO we will provide major insights about mechanisms that facilitate the evolution of cooperation.