The toughest organisms on Earth, called extreme creatures, can survive extreme conditions such as extreme dryness (dryness), extreme cold, space vacuum, acidic or high-level radiation. The toughest so far seems to be the bacteria Deinococcus radiodurans. It can withstand a thousand times more radiation than a lethal dose to humans. But until now, scientists have wondered how radio resistance could evolve in many organisms on Earth that are naturally protected from solar radiation by magnetic fields. Some scientists have suggested that the radiation resistance of extreme organisms can evolve alongside other types of resistance, such as resistance to drying, but which genes are specifically involved in radiation resistance?
To address this problem, Dr. Cox’s team at the University of Wisconsin-Madison decided to “let the cells speak to them.” The researchers started with E. coli, a naturally resistant bacterium, and exposed them to repeated high-level irradiation cycles. After several radiation exposures and growth, a small number of groups that resist radiation have emerged. Using whole genome sequencing, researchers Genetic change We identified which mutations are present in each radioactive population and which mutation gives the bacteria radioactive resistance.
In the first study, Dr. The Cox team started by exposing E. coli to 50 ionizations (Bruckbauer et al 2019b). Some radiation-resistant populations appeared over about 10 episodes, and after 50 episodes, a study of the gene profile highlighted the three mutations responsible for radiation resistance. They are all genes involved in DNA repair mechanisms. In a new study here, the team exposed the bacteria to more than 50 radiation exposures and selections.
Published results Pioneer in microbiology It shows that the population of radiation-resistant E. coli continues to evolve and subpopulations have emerged. Surprisingly, the radio resistance induced by the first series of ionization can be primarily associated with three mutations, but the second caused hundreds of mutations, including large-scale deletion and replication of several genes. “In this new experiment, the four populations we are evolving have now achieved levels of radio resistance close to those found in Deinococcus radiodurans. As the current experiment progresses, genome changes have proven to be far more complex than expected. .” Dr. Cox says.
This time it is more difficult to pinpoint all the mutations that contribute to the increase in radiation resistance, but researchers show that more cellular metabolism is affected (ATP synthesis, iron-sulfur cluster generation, cadaverine synthesis, and reactive oxygen species reaction). . In addition, this study demonstrates that radio resistance can develop to the level of Deinococcus radiodurans independently of drying resistance. As the explanation of radiation and its experimental evolution continue, more data are collected on how to induce radio resistance in bacteria. This can one day become a valuable toolbox. Mutation For example, they design radiation-resistant probiotics that help patients treated with radiation therapy or astronauts exposed to space. radiation.
Pioneer in microbiology, DOI: 10.3389 / fmicb.2020.582590 , www.frontiersin.org/articles/1… 2020.582590 / abstract
Summons: The evolution of radio resistance is more complex than previously thought, retrieved on September 22, 2020 at https://phys.org/news/2020-09-evolution-radio-resistance-complicated-previously-thought.html (2020, September 22).
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