In a thin glass chamber filled with water, life is boiling over: millions of tiny bacteria Thiovulum sp. ST, freshly isolated from a natural spring, start moving as a single organism. At first, they are evenly distributed, but within a few minutes the water begins to stir — large vortices appear, just like those in a pot of soup heating up on the stove.
Each bacterium is a tiny swimmer with its own "motor" (a flagellum). It senses where oxygen is more abundant and swims there — this is called chemotaxis. At the same time, the bacterium is denser than water and tends to settle toward the bottom — this is gravitaxis. When millions of such swimmers come together, their individual motions combine into a powerful collective flow. The upper layers, richer in oxygen, attract bacteria from below; these, in turn, drag water along, and convective cells swirl in the chamber, like in boiling broth.
These flows are not just pretty — they help the colony survive. By mixing the water, the bacteria bring fresh oxygen and nutrients closer and flush away waste. It becomes a self-sustaining system: motion creates conditions for life, and life sustains motion. A video of this work won an award at the American Physical Society's scientific video competition in 2025.
Thiovulum bacteria are among the fastest swimmers among microbes: in one second, they can cover a distance tens of times their own body length. If a human swam at the same relative speed, they would cross an Olympic-size pool in a couple of seconds.
The collective motion of microbes creating visible currents evokes sci-fi plots about intelligent swarms or "liquid life" — for instance, in Stanislaw Lem's novel "Solaris," the ocean behaves as a single organism even though it is made of countless elements.