Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How Do Bacteria Swim?

24.11.2008
Brown Physicists Explain

Brown University physicists have completed the most detailed study of the swimming patterns of a microbe, showing for the first time how its movement is affected by drag and a phenomenon called Brownian motion. The findings appear online this week in the Proceedings of the National Academy of Sciences.

Imagine yourself swimming in a pool: It’s the movement of your arms and legs, not the viscosity of the water, that mostly dictates the speed and direction that you swim.

For tiny organisms, the situation is different. Microbes’ speed and direction are subjected more to the physical vagaries of the fluid around them.

“For bacteria to swim in water,” explained Jay Tang, associate professor of physics at Brown University, “it’s like us trying to swim through honey. The drag is dominant.”

Tang and his team at Brown have just completed the most detailed study of the swimming patterns of one particular bacterium, Caulobacter crescentus. In a paper published online this week in the Proceedings of the National Academy of Sciences (in print Nov. 25), the researchers show how this microbe’s movement is affected by drag and a phenomenon called Brownian motion. The observations would appear to hold true for many other bacteria, Tang said, and shed light on how these organisms scavenge for food and how they approach surfaces and “stick” to them.

Caulobacter is a single-celled organism with a filament-like tail called a flagellum. As it swims, its rounded cellular head rotates in one direction, while the tail rotates in the opposite direction. This creates torque, which helps explain the bacterium’s nonlinear movement through a fluid. What Tang and his team found, however, is that Caulobacter also is influenced by Brownian motion, which is the zigzagging motion that occurs when immersed particles are buffeted by the actions of the molecules of the surrounding medium. What that means, in effect, is that Caulobacter is being pinballed by the water molecules surrounding it as it swims.

This twin effect of hydrodynamic interaction and Brownian motion governs the circular swimming patterns of Caulobacter and many other microorganisms, the scientists found.

“Random forces are always more important the smaller the object is,” said Tang, whose team included Guanglai Li, assistant professor of physics (research) at Brown, and Lick-Kong Tam, a recent Brown graduate who is now studying biomedical engineering at Yale University. “At Caulobacter’s size, the random forces become dominant.”

The researchers also discovered another clue to the swimming behavior: Caulobacter’s swimming circles grew tighter as the bacterium got closer to a surface boundary, in this case a glass slide. The tighter circle, the team found, is the result of more drag being exerted on the microbe as it swims closer to the surface. When the microbe was farther away from the surface, it encountered less drag, and its swimming circle was wider, the group learned.

It’s this zigzagging effect that helps explain why “most of the time, these cells are not as close to the surface as they are predicted to be,” Tang said. “The reason is Brownian motion, because they are jumping around.”

That finding is important, because it helps explain the feedings areas for simple-celled organisms. Perhaps more importantly, it may help scientists understand how bacteria ultimately arrive at a surface and adhere to it. The applications range from better understanding the flow and adhesion of platelets in the bloodstream to greater insights into how contaminants are captured as they percolate through the soil.

“As it turns out, swimming is an important mechanism to that adhesion process,” Tang said.

The National Institutes of Health and the National Science Foundation funded the work.

Richard Lewis | EurekAlert!
Further information:
http://www.Brown.edu

More articles from Physics and Astronomy:

nachricht New thruster design increases efficiency for future spaceflight
16.08.2017 | American Institute of Physics

nachricht Tracking a solar eruption through the solar system
16.08.2017 | American Geophysical Union

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

Im Focus: Scientists improve forecast of increasing hazard on Ecuadorian volcano

Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, the Italian Space Agency (ASI), and the Instituto Geofisico--Escuela Politecnica Nacional (IGEPN) of Ecuador, showed an increasing volcanic danger on Cotopaxi in Ecuador using a powerful technique known as Interferometric Synthetic Aperture Radar (InSAR).

The Andes region in which Cotopaxi volcano is located is known to contain some of the world's most serious volcanic hazard. A mid- to large-size eruption has...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

New thruster design increases efficiency for future spaceflight

16.08.2017 | Physics and Astronomy

Transporting spin: A graphene and boron nitride heterostructure creates large spin signals

16.08.2017 | Materials Sciences

A new method for the 3-D printing of living tissues

16.08.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>