Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Microscopic "Clutch" Puts Flagellum in Neutral

23.06.2008
A tiny but powerful engine that propels the bacterium Bacillus subtilis through liquids is disengaged from the corkscrew-like flagellum by a protein clutch, Indiana University Bloomington and Harvard University scientists have learned. Their report appears in this week's Science.

Scientists have long known what drives the flagellum to spin, but what causes the flagellum to stop spinning -- temporarily or permanently -- was unknown.

"We think it's pretty cool that evolving bacteria and human engineers arrived at a similar solution to the same problem," said IU Bloomington biologist Daniel Kearns, who led the project. "How do you temporarily stop a motor once it gets going?"

The action of the protein they discovered, EpsE, is very similar to that of a car clutch. In cars, the clutch controls whether a car's engine is connected to the parts that spin its wheels. With the engine and gears disengaged from each other, the car may continue to move, but only because of its prior momentum; the wheels are no longer powered.

... more about:
»Biofilm »EPSE »Kearns »flagellum »subtilis

EpsE is thought to "sit down," as Kearns describes it, on the flagellum's rotor, a donut-shaped structure at the base of the flagellum. EpsE's interaction with a rotor protein called FliG causes a shape change in the rotor that disengages it from the flagellum's proton-powered engine.

The discovery of EpsE and its function was accidental. Kearns and colleagues were actually interested in learning more about the genes that cause individual cells of B. subtilis to cease wandering in solitude and take up residence in a massively communal, stationary assemblage called a biofilm. The stability of biofilms can be jeopardized by hyperactive bacterial cells whose flagella continue to spin.

"We were trying to get at how the bacterium's ability to move and biofilm formation are balanced," Kearns said. "We were looking for the genes that affected whether the cells are mobile or stationary. Although B. subtilis is harmless, biofilms are often associated with infections by pathogenic bacteria. Understanding biofilm formation may eventually prove useful in combating bacterial infections."

Once the scientists learned EpsE was involved in repressing flagellar motion, they devised two possible explanations for how EpsE acts. The first was that EpsE acts like a brake by pushing a non-moving part against a moving part and locking up the works. The other possibility, they imagined, was that EpsE acts like a clutch, disengaging one moving part from another. In this latter scenario, the engine can no longer drive flagellar spinning because key moving parts are no longer in contact. In this case, the flagellum would still have freedom of motion, listless as it might be.

To determine which hypothesis was correct, the scientists decided it best to let the tail wag the dog. They attached the tail end of the flagellum to a glass slide and examined the movement of the entire cell in the presence and absence of EpsE. In the absence of EpsE, the entire cell rotated once every five seconds. In the presence of EpsE, the cells stopped but could rotate passively, pushed by disturbances in the environment (Brownian motion). If EpsE acted like a brake, the cells would not have rotated at all.

The researchers also learned that when the cell begins producing EpsE, it takes about 15 minutes before the flagellar machinery is disabled.

"This makes a lot of sense as far as the cell is concerned," Kearns said. "The flagellum is a giant, very expensive structure. Often when a cell no longer needs something, it might destroy it and recycle the parts. But here, because the flagellum is so big and complex, doing that is not very cost effective. We think the clutch prevents the flagellum from rotating when constrained by the sticky matrix of the biofilm."

The discovery may give nanotechnologists ideas about how to regulate tiny engines of their own creation. The flagellum is one of nature's smallest and most powerful motors -- ones like those produced by B. subtilis can rotate more than 200 times per second, driven by 1,400 piconewton-nanometers of torque. That's quite a bit of (miniature) horsepower for a machine whose width stretches only a few dozen nanometers.

IU Bloomington Biology Research Associate Kris Blair is the paper's lead author. IUB undergraduate student Jared Winkelman and Harvard University microbiologists Linda Turner and Howard Berg also contributed to the report. It was funded with a grant from the National Science Foundation (Kearns) and the National Institutes of Health (Berg).

To speak with Kearns, please contact David Bricker, University Communications, at 812-856-9035 or brickerd@indiana.edu.

David Bricker | newswise
Further information:
http://www.indiana.edu

Further reports about: Biofilm EPSE Kearns flagellum subtilis

More articles from Life Sciences:

nachricht One step closer to reality
20.04.2018 | Max-Planck-Institut für Entwicklungsbiologie

nachricht The dark side of cichlid fish: from cannibal to caregiver
20.04.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>