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 A study demonstrates that p38 protein regulates the formation of new blood vessels
17.07.2019 | Institute for Research in Biomedicine (IRB Barcelona)

nachricht For bacteria, the neighbors co-determine which cell dies first: The physiology of survival
17.07.2019 | Technische Universität München

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Megakaryocytes act as „bouncers“ restraining cell migration in the bone marrow

Scientists at the University Würzburg and University Hospital of Würzburg found that megakaryocytes act as “bouncers” and thus modulate bone marrow niche properties and cell migration dynamics. The study was published in July in the Journal “Haematologica”.

Hematopoiesis is the process of forming blood cells, which occurs predominantly in the bone marrow. The bone marrow produces all types of blood cells: red...

Im Focus: Artificial neural network resolves puzzles from condensed matter physics: Which is the perfect quantum theory?

For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.

Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...

Im Focus: Extremely hard yet metallically conductive: Bayreuth researchers develop novel material with high-tech prospects

An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".

The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...

Im Focus: Modelling leads to the optimum size for platinum fuel cell catalysts: Activity of fuel cell catalysts doubled

An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.

Fuel cells may well replace batteries as the power source for electric cars. They consume hydrogen, a gas which could be produced for example using surplus...

Im Focus: The secret of mushroom colors

Mushrooms: Darker fruiting bodies in cold climates

The fly agaric with its red hat is perhaps the most evocative of the diverse and variously colored mushroom species. Hitherto, the purpose of these colors was...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

Tracking down climate change with radar eyes

17.07.2019 | Earth Sciences

Researchers build transistor-like gate for quantum information processing -- with qudits

17.07.2019 | Information Technology

A new material for the battery of the future, made in UCLouvain

17.07.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>