Featured Research

from universities, journals, and other organizations

E. Coli Bacteria Make Alzheimer’s-Linked Fibers

Date:
February 1, 2002
Source:
Washington University School Of Medicine
Summary:
Fibers known to be important in Alzheimer’s disease also are produced by bacteria that cause ailments such as urinary tract infections, according to research at Washington University School of Medicine in St. Louis. The finding is described in the February 1 issue of the journal Science.

Fibers known to be important in Alzheimer’s disease also are produced by bacteria that cause ailments such as urinary tract infections, according to research at Washington University School of Medicine in St. Louis. The finding is described in the February 1 issue of the journal Science.

Related Articles


Scott J. Hultgren, Ph.D., the Helen Lehbrink Stoever Professor of Molecular Microbiology, led the study; Matthew R. Chapman, Ph.D., post-doctoral fellow in molecular microbiology was first author.

The scientists found that certain strains of the bacterium Escherichia coli (E. coli) produce amyloid fibers similar to those that can accumulate in the brain to form senile plaques, a hallmark of Alzheimer’s disease. The bacterial fibers, known as curli, form a meshwork around the bacteria, joining them together in clusters or communities known as biofilms. Bacteria in biofilms are more resistant to antibiotics and to the body’s immune defenses.

The discovery marks the first time that amyloid has been found in bacteria. Previously, amyloid was thought to be made only by cells of higher organisms. Even then, their presence was regarded as a mistake, a biological error.

“This is the first example of a dedicated molecular machinery to produce amyloid and thus shows that amyloid production is not always a mistake,” says Hultgren. “This finding gives us a powerful genetic system to study the molecular details of amyloid formation and may allow us to begin designing drugs that will block the formation of amyloid or treat or prevent human amyloid diseases.”

Salmonella bacteria also produce bacterial amyloid or curli, and the genes for curli production exist in other bacteria, as well, says Chapman. The process of curli production is similar to the formation of a snowflake on a dust particle. The particle is a nucleus that triggers the precipitation of ice crystals at its surface, setting off a chain reaction that leads to more ice crystals and growth of the snowflake.

Curli production in E. coli involves two main proteins, CsgA and CsgB. The A protein is released by the bacteria dissolved in the surrounding fluid. The B molecule is embedded in the wall of the bacterium and is exposed to the outside. Like dust particles in snowflake production, each B protein is a nucleus that triggers the precipitation of dissolved A-proteins. As the A proteins pop out of solution they join together and align into curli fibers, with each fiber attached to a B protein.

The finding also raises the important question of whether bacterial infections play some role in amyloid diseases, including Alzheimer’s disease.

Human amyloid diseases also are thought to involve dissolved amyloid proteins that undergo a change in shape and aggregate into fibers, says Hultgren. When those fibers develop in the brain, it leads to Alzheimer’s disease. According to Hultgren, “the question is, what causes the soluble protein in human disease to convert into amyloid fibers? We can now study that mechanism in E. coli.”

Hultgren and Chapman speculate that bacterial infections could play a role in the development of amyloid plaques in Alzheimer’s disease and other amyloid diseases in at least two ways.

“Bacteria might contribute directly to plaque formation through the amyloid they produce,” says Chapman, “or they might contribute indirectly by triggering the precipitation of amyloid precursor proteins already present in the body.” Hultgren and his research team also are working to crystallize the combined A and B proteins to visualize how the two molecules interact.

“Learning that bacteria produce amyloid is a revelation,” says Paul Berg, Cahill Professor of Cancer Research and Biochemistry, Emeritus, at Stanford University School of Medicine and winner of the 1980 Nobel Prize in Chemistry.

“That discovery provides an additional vantage point from which to assess the role of amyloid production and accumulation in Alzheimer's disease and related neuro-pathologies. Hopefully, this model will reveal clues for preventing the devastating formation of amyloid plaques characteristic of those diseases."


Story Source:

The above story is based on materials provided by Washington University School Of Medicine. Note: Materials may be edited for content and length.


Cite This Page:

Washington University School Of Medicine. "E. Coli Bacteria Make Alzheimer’s-Linked Fibers." ScienceDaily. ScienceDaily, 1 February 2002. <www.sciencedaily.com/releases/2002/02/020201080207.htm>.
Washington University School Of Medicine. (2002, February 1). E. Coli Bacteria Make Alzheimer’s-Linked Fibers. ScienceDaily. Retrieved November 29, 2014 from www.sciencedaily.com/releases/2002/02/020201080207.htm
Washington University School Of Medicine. "E. Coli Bacteria Make Alzheimer’s-Linked Fibers." ScienceDaily. www.sciencedaily.com/releases/2002/02/020201080207.htm (accessed November 29, 2014).

Share This


More From ScienceDaily



More Mind & Brain News

Saturday, November 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Tryptophan Isn't Making You Sleepy On Thanksgiving

Tryptophan Isn't Making You Sleepy On Thanksgiving

Newsy (Nov. 27, 2014) — Tryptophan, a chemical found naturally in turkey meat, gets blamed for sleepiness after Thanksgiving meals. But science points to other culprits. Video provided by Newsy
Powered by NewsLook.com
Are Female Bosses More Likely To Be Depressed?

Are Female Bosses More Likely To Be Depressed?

Newsy (Nov. 24, 2014) — A new study links greater authority with increased depressive symptoms among women in the workplace. Video provided by Newsy
Powered by NewsLook.com
Winter Can Cause Depression — Here's How To Combat It

Winter Can Cause Depression — Here's How To Combat It

Newsy (Nov. 23, 2014) — Millions of American suffer from seasonal depression every year. It can lead to adverse health effects, but there are ways to ease symptoms. Video provided by Newsy
Powered by NewsLook.com
Could Your Genes Be The Reason You're Single?

Could Your Genes Be The Reason You're Single?

Newsy (Nov. 21, 2014) — Researchers in Beijing discovered a gene called 5-HTA1, and carriers are reportedly 20 percent more likely to be single. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins