Under the microscope, strong-swimming swamp bacteria spontaneously organize into crystals

April 6, 2015, Rockefeller University
Under the microscope, strong-swimming swamp bacteria spontaneously organize into crystals
Thiovulum cells cluster together to form a repeating pattern known hexagonal lattice. It is the densest geometrical arrangement for things of uniform size, and it appears frequently in nature, in bees' honeycomb, for example. Credit: The Laboratory of Condensed Matter Physics at Rockefeller University/Physical Review Letters

Insects form swarms, fish school, birds flock together. Likewise, one species of bacteria forms dynamic, living crystals, says new research from Rockefeller University. Biophysicists have revealed that fast-swimming, sulfur-eating microbes known as Thiovulum majus can organize themselves into a two-dimensional lattice composed of rotating cells, the first known example of bacteria spontaneously forming such a pattern.

"The regular, repeated arrangement of the microbial cells shares the geometry of atoms within a mineral crystal, but the dynamics are fundamentally different; the bacterial constantly move and reorganize as a result of the power generated by individual cells within them," says study author Albert Libchaber, Detlev W. Bronk Professor and head of the Laboratory of Experimental Condensed Matter Physics.

The single cells' rotating motion—which forms the crystals by drawing in other cells and then powers the crystals' own motion—led the researchers to dub them "microscopic tornadoes" in a paper published April 6 in Physical Review Letters.

It's no coincidence that Thiovulum majus is among the fastest swimming bacteria known. Capable of moving up to 60 body lengths per second while rotating rapidly, these microbes propel themselves using whip-like flagella that cover their surfaces. But in its natural habitat, deep in marsh water, these microbes don't travel much. They tether themselves to a surface and use their flagella to generate a current strong enough to pull in the nutrients they need: sulfides from rotting organic matter and oxygen used to burn the sulfides.

The rotation of individual Thiovulum cells attracts nearby cells, causing them to cluster in a lattice, or crystalline pattern. The motion of the cells in turn powers the motion of the crystals, which continually to reorganize. Credit: The Laboratory of Experimental Condensed Matter Physics at Rockefeller University

What one cell can do, many can do much better, and in previous work, Libchaber and postdoc Alexander Petroff examined how groups of tethered Thiovulum organize and reorganize themselves so as to pull in more nutrients.

"Because this microbe can generate so much force with its flagella, we became curious about what dynamics might emerge when many swim freely together," Petroff says of the investigation, which began when study co-author Xiao-Lun Wu, of the University of Pittsburg, was visiting. "After we put an enriched culture of Thiovulum under a microscope, this beautiful structure appeared."

Researchers set about determining the balance of physical forces that explain how the microbes organize themselves into crystals. When placed in an observation chamber within a microscope slide, the microbes swam either up or down until they collided with the glass. But even then, they kept on swimming, like flies trying to escape through a closed window, Petroff says.

Swimming in place, the cells draw water toward, then up and around themselves, creating a tornado-like flow. This flow pulls in nearby cells, which cluster together in a shifting two-dimensional lattice that is similar to the three-dimensional pattern that defines crystals. Within the lattice, each cell has six immediate neighbors, creating a hexagonal pattern that appears frequently in nature, including among penguins packing together for warmth and in the chambers of honeycomb. It is the densest way to pack things of a uniform size.

But the bacterial crystal continues to reorganize and melt, animated by the ' rotating motion, which causes the microbes to shift against one another, in much the same way that gravity pulls sand grains down the sides of a pile.

It's not clear why the form these crystals, or even if they do so in habitats outside of microscope slides. But the coherent group behavior responsible for generating the crystals is a common phenomenon, known as collective dynamics.

"Usually, when birds, insects, fish, or even bacteria move together in a coordinated fashion, you see coherent motion on the scale of the group, but disorder at the level of the individual," Libchaber says. "This is not so for Thiovulum. Instead of turbulent movement, the form extremely regular crystalline structures. It appears that Thiovulum crystals represent a new form of collective dynamics."

Explore further: Scientists combine bacteria with liquid crystals

Related Stories

Scientists combine bacteria with liquid crystals

March 6, 2014

(Phys.org) —When swimming around, bacteria aren't good with the "pool rules."  In small quantities, they'll follow the lanes, but put enough together and they'll begin to create their own flow.

Researchers explain emergence of bacterial vortex

June 23, 2014

When a bunch of B. subtilis bacteria are confined within a droplet of water, a very strange thing happens. The chaotic motion of all those individual swimmers spontaneously organizes into a swirling vortex, with bacteria ...

Cells target giant protein crystals for degradation

March 12, 2015

Researchers at the RIKEN Brain Science Institute in Japan engineered a fluorescent protein that rapidly assembles into large crystals inside living cells, and showed that cells actively targeted the crystals for degradation. ...

Swimming algae offer insights into living fluid dynamics

March 27, 2015

None of us would be alive if sperm cells didn't know how to swim, or if the cilia in our lungs couldn't prevent fluid buildup. But we know very little about the dynamics of so-called "living fluids," those containing cells, ...

Harnessing the power of microbes as therapeutics

March 30, 2015

A new report recently released by the American Academy of Microbiology discusses how specific microbes can be modified to enhance their therapeutic potential for treating human diseases such as cancer and antibiotic resistant ...

Recommended for you

Walking crystals may lead to new field of crystal robotics

February 23, 2018

Researchers have demonstrated that tiny micrometer-sized crystals—just barely visible to the human eye—can "walk" inchworm-style across the slide of a microscope. Other crystals are capable of different modes of locomotion ...

Recurrences in an isolated quantum many-body system

February 23, 2018

It is one of the most astonishing results of physics—when a complex system is left alone, it will return to its initial state with almost perfect precision. Gas particles, for example, chaotically swirling around in a container, ...

Seeing nanoscale details in mammalian cells

February 23, 2018

In 2014, W. E. Moerner, the Harry S. Mosher Professor of Chemistry at Stanford University, won the Nobel Prize in chemistry for co-developing a way of imaging shapes inside cells at very high resolution, called super-resolution ...

Hauling antiprotons around in a van

February 22, 2018

A team of researchers working on the antiProton Unstable Matter Annihilation (PUMA) project near CERN's particle laboratory, according to a report in Nature, plans to capture a billion antiprotons, put them in a shipping ...

Urban heat island effects depend on a city's layout

February 22, 2018

The arrangement of a city's streets and buildings plays a crucial role in the local urban heat island effect, which causes cities to be hotter than their surroundings, researchers have found. The new finding could provide ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.