How a Microbe Swims Without Arms or Legs ✛ ✦

Original: "Growing, Buckling, and Swirling: motility from polymerization"

· Naveen Kumar D, Michael J. Shelley, Brato Chakrabarti

arXiv:2607.10446 · 2026-07-11 · CC BY 4.0 · 1 min

By sprouting threads on its surface, a microbe rolls through liquid like a fuzzy ball, propelled by its own growth.

In a fluid as thick as syrup, a microbe turns into a fuzzy ball. From its surface, ultra-thin threads shoot out, like microscopic harpoons. The push from each newly grown thread propels the cell forward. The pattern of growth points controls movement, like tuning rocket nozzles: by varying their arrangement, you can make the ball spin, swim straight, or spiral. With computer simulations, scientists confirmed this mechanics. Thread growth increases disorder — par for the course in living systems.

The bacterium Acetobacter xylinum, which creates the film in kombucha, grows cellulose fibers longer than its body and rolls like a fuzzy ball.

Slow but steady movement is a potential biosignature in alien oceans.

The principle of force addition, or the superposition principle, works everywhere: from magnetic reconnection on the Sun to accretion disks around active galactic nuclei. Engineers are studying this strategy for programmable nanobots. Thread symmetry, per Emmy Noether's laws, dictates the movement direction.

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The bacterium Acetobacter xylinum can grow cellulose fibers several times longer than its own body and, pushing off them against the fluid, roll like a tiny fuzzy ball.

Programmable microswimmers evoke the smart-dust swarm from Lem's 'The Invincible,' where tiny robots' behavior is set by the pattern on their hulls.

\bar{\sigma} > \chi + \frac{\bar{\lambda} + 1}{\bar{\rho}}

The dimensionless activity σ̄ must exceed the sum of elastic resistance χ and catastrophe rate (λ̄) normalized by filament density (ρ̄). When this inequality is satisfied, the carpet loses stability and begins to buckle, generating macroscopic flows.

Concepts

microbial collective motion polymer flagella microswimmer microorganism swimming dynamics active matter self assembly surface tension patterned fluid dynamics collective cell migration entropy driven self assembly frame dragging protein folding galaxy growth mechanisms biofilm crystallization principle of least action vibration Archimedes' principle topological pattern formation

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How a Microbe Swims Without Arms or Legs ✛ ✦