The emergent properties of diverse organism ensembles: from slime molds to protocells

Abstract

Many crucial features of biological systems emerge from self-organized patterns.Moreover, to understand ecological succession and evolutionary change in systems with emergent properties, we must contend with how self-organized patterns are affected by individuals that follow divergent interaction rules. Here we use cellular slime molds as a model system to investigate emergent biological properties in the context of heterogeneous individuals. Slime molds have a complex life cycle with a unicellular foraging stage and a multicellular dispersal stage. First, we show that slime mold cells spontaneously self-organize into cells that aggregate and follow multicellular development and loner cells that stay behind. We then theoretically explore the ecological consequences of this self-organized partitioning in the context of differentially aggregative strains. Second, we show that self-organization also plays a role in the foraging stage of the slime mold life cycle. Cells spontaneously partition into fast, polarized cells and slow unpolarized cells. This behavioral differentiation powers the expansion of the slime mold colony and determines the outcomes of their interaction with bacterial prey. Altogether we reveal that individual behavioral variation is often the result of self-organization but also determines further self-organized patterns that feed into the emergent properties of the system. Third, we look at a different system altogether — early chromosomes in protocells — and show that competition between genes with different replication efficiencies might have driven the organization of the genome into chromosomes.