Abstract

At the microscopic scale, virtually everything moves. From these diverse patterns of movement, one might hope to distinguish living from non-living matter, bacteria from eukaryotes, random from directed, purposeful movement. In this talk I will discuss our recent work on phenotyping the motility of diverse microeukaryotes from long-time trajectory statistics. These include microswimmers that orchestrate propulsion-generating appendages (cilia and flagella) for swimming through fluids, as well as organisms that glide mysteriously on surfaces without the need to resort to any appendages at all. We present and derive species-agnostic measures of active motility from high-speed live imaging experiments. We show how to distinguish between distinct yet stereotyped states (or gaits) of activity, and demonstrate how environmental cues (e.g. physical confinement, light, chemicals) induce systems-level cellular signalling whose effect becomes measurable in terms of transition probabilities between states. Finally, we speculate on the implications of these findings for the evolution of cellular decision making in basal eukaryotes.