Featured Research

from universities, journals, and other organizations

Scientists Uncover Break-And-Entry Strategy Of Disease-Causing Bacteria

Date:
January 12, 2001
Source:
Washington University School Of Medicine
Summary:
As bacteria become resistant to current antibiotics, scientists are searching for the root causes of infection in order to develop more effective treatments. Researchers at Washington University School of Medicine in St. Louis have come one step closer to understanding how bacteria such as Streptococcus and Staphylococcus operate: These pathogens introduce their toxins by punching holes in the host-cell membrane.

St. Louis, Jan. 12, 2001 —- As bacteria become resistant to current antibiotics, scientists are searching for the root causes of infection in order to develop more effective treatments. Researchers at Washington University School of Medicine in St. Louis have come one step closer to understanding how bacteria such as Streptococcus and Staphylococcus operate: These pathogens introduce their toxins by punching holes in the host-cell membrane. The cover of the Jan. 12 issue of Cell features the research. Scientists have made great strides in understanding how Gram-negative bacteria, such as Salmonella and E. coli, infiltrate host cells and establish infection. However, a second class of bacteria called Gram-positive causes human diseases such as strep throat, necrotizing faciitis, toxic shock syndrome and rheumatic fever. "Gram-positive organisms are responsible for five of the top six bacterial infections that are now resistant to multiple antibiotics available today," says study leader Michael G. Caparon, Ph.D., associate professor of molecular microbiology.

The first authors of the study are M.D./Ph.D. student John C. Madden and Natividad Ruiz, Ph.D., now at Princeton University.

Gram-negative bacteria inject previously healthy cells with toxins that disrupt essential processes. Several laboratories have visualized needle-like projections from these bacteria into host cells. Presumably, the projections serve as syringes.

Caparon and colleagues discovered that Gram-positive bacteria use an equivalent technique. Most Gram-positive pathogens contain proteins called cholesterol-dependent cytolysins (CDC). Because these molecules have persisted throughout the evolution of this diverse group, they might play a critical role in infection, the researchers surmised.

Studying the molecular basis of infection has been difficult in the past. But thanks to improved techniques, Caparon’s group was able to manipulate the bacteria genetically. The researchers made defined mutants of Streptococcus pyogenes, the Gram-positive, flesh-eating bacterium that also causes strep throat and impetigo. By studying the consequences of the genetic defects, they uncovered specific points in the infection pathway.

S. pyogenes contains a CDC called streptolysin O (SLO). The researchers found that this protein chips away at the outer membranes of targeted cells, creating large holes or pores. SLO does not enter cells, however. Instead, a protein called SPN (S. pyogenes NAD-glycohydrolase) gets into cells after SLO has done its work. "SLO appears to pave the way for the entry of SPN, which is useless outside cells," Caparon says. "Once inside, SPN manipulates certain cellular processes."

His group hopes to determine how SPN affects host cells. Once scientists learn exactly how Gram-positive bacteria cause disease, they can step back and see where they can intervene. "New classes of current antibiotics simply buy us a little time. We have to come up with new ways of thinking about the problem," Caparon says.

Madden JC, Ruiz N, Caparon M. Cytolysin-mediated translocation (CMT): A functional equivalent of Type III Secretion in Gram-positive bacteria. Cell, vol. 104 pp. 1-20, Jan. 12, 2001.

Funded by Public Health Service Grants from the National Institutes of Health.


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. "Scientists Uncover Break-And-Entry Strategy Of Disease-Causing Bacteria." ScienceDaily. ScienceDaily, 12 January 2001. <www.sciencedaily.com/releases/2001/01/010111194856.htm>.
Washington University School Of Medicine. (2001, January 12). Scientists Uncover Break-And-Entry Strategy Of Disease-Causing Bacteria. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2001/01/010111194856.htm
Washington University School Of Medicine. "Scientists Uncover Break-And-Entry Strategy Of Disease-Causing Bacteria." ScienceDaily. www.sciencedaily.com/releases/2001/01/010111194856.htm (accessed September 19, 2014).

Share This



More Plants & Animals News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Chimp Violence Study Renews Debate On Why They Kill

Chimp Violence Study Renews Debate On Why They Kill

Newsy (Sep. 17, 2014) The study weighs in on a debate over whether chimps are naturally violent or become that way due to human interference in the environment. Video provided by Newsy
Powered by NewsLook.com
Some Tobacco Farmers Thrive Amid Challenges

Some Tobacco Farmers Thrive Amid Challenges

AP (Sep. 16, 2014) The South's tobacco country is surviving, and even thriving in some cases, as demand overseas keeps growers in the fields of one of America's oldest cash crops. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

AFP (Sep. 16, 2014) Scientists say a female colossal squid weighing an estimated 350 kilograms (770 lbs) and thought to be only the second intact specimen ever found was carrying eggs when discovered in the Antarctic. Duration: 00:47 Video provided by AFP
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:
from the past week

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