Effect of Hydrodynamic Regime on Snowflake Yeast Evolution

Abstract

Experimental evolution of S. cerevisiae has unlocked new avenues in the study of the transition from uni- to multicellularity and how selection moves from the level of the individual cell to the multicellular-level. Selection for large size, proxied by selecting for settling speed, quickly leads to clusters of cells, coined ‘snowflake yeast’, and adaptations at the cluster level. While selecting for settling speed is a good proxy for selection of large size because it is simple to implement, settling, or sedimentation, is a complex process with the potential for unforeseen impacts on this model system. By changing the hydrodynamic regime during settling speed selection, the selection process, and its effects on the snowflake yeast system other than selection for increased size, is explored. It is found that size distributions change in response to differing hydrodynamic regimes during settling speed selection. However, the path to larger size remains relatively constant, showing that the major findings of the snowflake yeast system are robust to changes in hydrodynamic regime during settling speed selection.