Abiogenesis is the process whereby life arose—or can arise—from nonliving matter. Somehow an assembly of chemicals containing information polymers bootstrapped itself up into a self-replicating system that grew in complexity over time. Rather little is known about how this chemical evolution can—and likely did—occur. This grant supports David Baum and David Beebe, Professors of Botany and of Biomedical Engineering, respectively, at the University of Wisconsin-Madison, in efforts to test the hypothesis that selection at the chemical ecosystem level—rather than at the level of individual molecules in a population—can yield ecosystems of (nucleic acid) information polymers that play complementary roles in promoting their collective propagation. Existing mathematical and computational models suggest that ecosystem-scale selection was important to abiogenesis. The term ‘selection’ refers to preferential survival owing to enhanced fitness in an environment. The term ‘ecosystem-scale selection’ refers to cases where the fitness serving as a basis for selection is a property of an ecosystem; here, a collection of chemicals. Ecosystem-scale selection naturally invokes the idea of a ‘container’ since containers offer a simple way of creating chemical systems that can compete with one another. In this project the container is an aqueous droplet; specifically, droplets containing different nucleic acid-based chemical systems that compete with one another for selection based on the droplets’ propensity to propagate (make more DNA/RNA). Some droplets will be discarded while others continue on in a series of experiments that allow the ecosystem in surviving droplets to evolve. The PIs aim to test the hypothesis that droplet-scale selection can lead to ecosystems of cooperating nucleic acid polymers that are particularly good at promoting their collective propagation. Baum and Beebe will perform experiments on various DNA/RNA ecosystems with an overall plan to create droplets containing a nucleic acid based chemical ecosystem, put the droplets through a series of incubate-select-propagate cycles, and then look for a response to selection by comparing the results of ‘selection’ and ‘control’ experiments. ‘Selection’ will be based on a fluorescent signal that indicates how much DNA/RNA has been synthesized and the bottom-lower-half droplets on the brightness scale will be discarded. Propagation will be achieved by splitting selected droplets in two and then fusing each ‘offspring’ droplet with a ‘food’ droplet. After a series of experimental cycles where droplets have been selected based on brightness, the PIs will turn to sequencing to rigorously determine whether there has been a selection effect by comparing the polymer-sequence-space obtained from droplet-selection experiments to the sequence-space of ‘control’ droplets (selected at random; irrespective of UV brightness). If successful, this project would provide the first direct experimental support for theoretical models which suggest that the emergence of cooperating sets of information polymers—and thus the genetic system of modern cells—is a result of selection on the emergent fitness of polymer-rich chemical ecosystems.