Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Common Worm Provides Insights Into Salmonella Virulence

08.06.2004


Using a common worm as a model, researchers from Duke University Medical Center have identified specific genes within Salmonella that give the bacteria its ability to infect host cells.


Alejandro Aballay, Ph.D.
CREDIT: Duke University Medical Center



They said their findings could ultimately lead to improved drugs to prevent or treat Salmonella infections.

The researchers found four genes related to the Salmonella’s "molecular syringe" that are required for the bacteria to have maximum potency in infecting the worm, known as Caenorhabditis elegans. The virulence factors -- injected into the host cells by Salmonella -- act by blunting the innate immune system of C. elegans from attacking and destroying the infecting bacteria.


These findings are important, the researchers said, because the C. elegans innate immune response to Salmonella infection is quite similar to that of mammals, including humans. For this reason, the researchers said that their C elegans model can provide new genetic insights into the relationships between invading microbes and their target host cells.

The results of the Duke experiments were published June 8, 2004, in the journal Current Biology. The research was supported by the National Institutes of Health and the Whitehead Institute for Biomedical Research.

"C elegans lives in the soil, so it continually comes into contact with bacteria and other microbes," said lead researcher microbiologist Alejandro Aballay, Ph.D. "It has a highly developed system for not only recognizing bacteria, but also responding to them. The ability of its innate immune system to respond appropriately to specific bacteria is very similar to that of mammals.

"The goal of our research is not only to better understand what makes a particular pathogen harmful for the host, but to determine those characteristics of the host that either make it resistant or susceptible to the pathogen," Aballay added. "To be successful in this type of research, one cannot just focus on the pathogen; the relationship between the pathogen and host is so important."

C elegans is an ideal model for genetic studies, Aballay said, because the worm takes only three days to develop from an embryo to an adult capable of reproducing. Also, scientists can easily manipulate specific genes in the worm, and as opposed to other animal models, large quantities of the animals can be grown quickly. They can even be frozen and used at a later date, Aballay said.

Additionally, the worm is essentially a long intestinal tract, which is also advantageous as a model for Salmonella virulence, since a primary target of Salmonella infections in mammals is the intestine. Aballay said this may be the reason of the remarkable overlap between Salmonella virulence factors required for pathogenesis in mammals and worms.

For their experiments, the team used the C. elegans-Salmonella enterica model developed by Aballay. Specifically, the researchers examined one of the bacteria’s five known "pathogenecity islands," or clusters of genes that have accumulated in S. enterica bacteria through time. These genes have been acquired by the bacteria through the course of evolution as a way of adapting and improving its chances of successfully infecting its hosts, Aballay explained.

"In this study we have related several genes located in pathogenicity islands to S. enterica pathogenesis in worms," Aballay said.

Within the pathogencity island 1 is the "molecular syringe," known as the Type III secretion system (TTSS). This TTSS punctures the cell wall of the host and injects the virulence factors inside. One of the specific virulence factors injected into the host cells through the TTSS, termed SptP, was critical for the Salmonella’s ability to kill C. elegans.

"While there are at least 13 effector proteins, or virulence factors, which are injected into the host through the TTSS, our studies have shown that a single protein (SptP) can have a major impact on an entire animal," Aballay explained. "What this factor does is diminish the animal’s ability to mount an effective immune response."

Aballay believes that this model opens news areas of research for better understanding the relationship between pathogens and host responses.

"While many virulence factors have been identified, the mechanisms by which they contribute to bacterial pathogenesis remain unknown," he said. "But with the identification of the targeted pathways in the host, we should be able to figure out how virulence factors influence the innate immune response."

Aballay said that the C elegans system could be an effective living model for testing or screening new compounds or drugs for treating Salmonella in humans. However, he added, much additional research in other living models is necessary before these new insights can be applied to human disease.

Using the C elegans model, Aballay and his colleagues are now conducting genetic screens to find genetic variants called polymorphisms in the host that appear to confer either resistance or susceptibility to Salmonella. The researchers expect that these polymorphisms would also play a role in human disease.

Other members of the research team were Duke’s Jennifer Tenor, as well as Beth McCormick, Ph.D., and Frederick Ausubel, Ph.D., of Harvard Medical School, Boston.

Richard Merritt | dukemed news
Further information:
http://dukemednews.org/news/article.php?id=7647

More articles from Life Sciences:

nachricht Nesting aids make agricultural fields attractive for bees
20.07.2017 | Julius-Maximilians-Universität Würzburg

nachricht The Kitchen Sponge – Breeding Ground for Germs
20.07.2017 | Hochschule Furtwangen

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

Leipzig HTP-Forum discusses "hydrothermal processes" as a key technology for a biobased economy

12.07.2017 | Event News

 
Latest News

Researchers create new technique for manipulating polarization of terahertz radiation

20.07.2017 | Information Technology

High-tech sensing illuminates concrete stress testing

20.07.2017 | Materials Sciences

First direct observation and measurement of ultra-fast moving vortices in superconductors

20.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>