  Propelling microorganisms through fluids and moving fluids along cellular
surfaces are essential biological functions accomplished by long, thin
structures called motile cilia and flagella, whose regular, oscillatory beating
breaks the time-reversal symmetry required for transport. Although top-down
experimental approaches and theoretical models have allowed us to broadly
characterize such organelles and propose mechanisms underlying their complex
dynamics, constructing minimal systems capable of mimicking ciliary beating and
identifying the role of each component remains a challenge. Here we report the
bottom-up assembly of a minimal synthetic axoneme, which we call a synthoneme,
using biological building blocks from natural organisms, namely pairs of
microtubules and cooperatively associated axonemal dynein motors. We show that
upon provision of energy by ATP, microtubules undergo rhythmic bending by
cyclic association-dissociation of dyneins. Our simple and unique beating
minimal synthoneme represents a self-organized nanoscale biomolecular machine
that can also help understand the mechanisms underlying ciliary beating.
