Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Radiation-resistant organism reveals its defense strategies

10.01.2003



The secret to its strength is a ring, Weizmann Institute researchers report in Science

Weizmann Institute scientists have found what makes the bacterium Deinococcus radiodurans the most radiation-resistant organism in the world: The microbe’s DNA is packed tightly into a ring. The findings, published in the January 10 issue of Science, solve a mystery that has long engaged the scientific community.

The red bacterium can withstand 1.5 million rads – a thousand times more than any other life form on Earth and three thousand that of humans. Its healthy appetite has made it a reliable worker at nuclear waste sites, where it eats up nuclear waste and transforms it into more disposable derivatives. The ability to withstand other extreme stresses, such as dehydration and low temperatures, makes the microbe one of the few life forms found on the North Pole. It is not surprising, then, that it has been the source of much curiosity worldwide, recently leading to a debate between NASA and Russian scientists – the latter saying that it originated on Mars, where radiation levels are higher.



Since DNA is the first part of a cell to be damaged by radiation and the most lethal damage is the breakage of both DNA strands, scientists have focused on DNA repair mechanisms to find the answer to the microbe’s resilience. Cells, including human cells, can mend only very few such breaks in their DNA. Microbes, for example, can repair only three to five. Yet D. radiodurans can fix more than 200. Thus scientists believed that the microbe must possess uniquely effective enzymes that repair DNA. However, a series of experiments showed that the microbe’s repair enzymes were very similar to those existing in ordinary bacteria.

Using an assortment of optical and electron microscopy methods, Prof. Avi Minsky of the Weizmann Institute of Science’s Organic Chemistry Department found that the microbe’s DNA is organized in a unique ring that prevents pieces of DNA broken by radiation from floating off into the cell’s liquids. Unlike other organisms, in which DNA fragments are lost due to radiation, this microbe does not lose genetic information because it keeps the severed DNA fragments tightly locked in the ring – by the hundreds, if necessary. The fragments, held close, eventually come back together in the correct, original order, reconstructing the DNA strands.

As exciting as these findings may be, they are not expected to lead to the protection of humans from radiation. “Our DNA is structured in a fundamentally different manner,” says Minsky. The results may, however, lead to a better understanding of DNA protection in sperm cells, where a ring-like DNA structure has also been observed.

More survival tricks

Minsky’s team also found that the microbe undergoes two phases of DNA repair. During the first phase the DNA fixes itself within the ring as described. It then performs an even more unusual stunt.

The bacterium is composed of four compartments, each containing one copy of DNA. Minsky’s group found two small passages between the compartments. After about an hour and a half of repair within the ring, the DNA unfolds and migrates to an adjacent compartment – where it mingles with the copy of DNA residing there. Then the “regular” repair machinery, common in humans and bacteria alike, comes into play – repair enzymes compare between the two copies of DNA, using each as a template to fix the other. Since the DNA has already been through one phase of repair in which many of the breaks are fixed, this phase can be completed relatively easily.

...and a backup system

The finding of a tightly packed ring made the team wonder how the bacterium could live and function under normal conditions. DNA strands must unfurl to perform their job of protein production. How can they do that if they can barely budge? This question led to the uncovering of another of the microbe’s survival strategies: out of the four copies of DNA, there are always two or three tightly packed in a ring while the other copies are free to move about. Thus at any given moment there are copies of DNA that drive the production of proteins and others that are inactive but continuously protected.

Minsky, along with other scientists, believes that the bacterium’s answer to acute stresses evolved on Earth as a response to the harsh environments from which it might have emerged. It is one of the few life forms found in extremely dry areas. The unique defense mechanism that evolved to help it combat dehydration proves useful in protecting it from radiation.

Deinococcus radiodurans was discovered decades ago in canned food that was sterilized using radiation. Red patches appeared in the cans – colonies of the bacterium – setting off questions as to how it could have survived. Though these questions have now been answered, the tide of speculation as to how these defense mechanisms evolved – and where – is likely to continue.


Prof. Abraham Minsky’s research is supported by Verband der Chemischen Industrie, Teva Pharmaceuticals, Israel, and the Helen & Milton A. Kimmelman Center for Biomolecular Structure & Assembly.

Prof. Minsky is the incumbent of the Professor T. Reichstein Professorial Chair.

The Weizmann Institute of Science in Rehovot, Israel, is one of the world’s top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,500 scientists, students, technicians and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials and developing new strategies for protecting the environment.

Jeffrey J. Sussman | EurekAlert!
Further information:
http://www.weizmann.ac.il/

More articles from Life Sciences:

nachricht Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

Im Focus: Newly proposed reference datasets improve weather satellite data quality

UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration

"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...

Im Focus: Repairing defects in fiber-reinforced plastics more efficiently

Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.

Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Solar Collectors from Ultra-High Performance Concrete Combine Energy Efficiency and Aesthetics

16.01.2017 | Trade Fair News

3D scans for the automotive industry

16.01.2017 | Automotive Engineering

Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs

16.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>