Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


How Do Bacteria Swim?

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:

More articles from Physics and Astronomy:

nachricht First results of NSTX-U research operations
26.10.2016 | DOE/Princeton Plasma Physics Laboratory

nachricht Scientists discover particles similar to Majorana fermions
25.10.2016 | Chinese Academy of Sciences Headquarters

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: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Greater Range and Longer Lifetime

26.10.2016 | Power and Electrical Engineering

VDI presents International Bionic Award of the Schauenburg Foundation

26.10.2016 | Awards Funding

3-D-printed magnets

26.10.2016 | Power and Electrical Engineering

More VideoLinks >>>