The evolution of radio-resistance is more complex than previously thought

The hardest organisms on Earth, called interphils, can survive extreme conditions such as extreme dryness, extreme cold, space vacuum, acid, or even high-level radiation. By far, the most difficult of all seems to be the bacterium Dinococcus radiodurus, which can withstand a dose of a thousand times more radiation than is fatal to humans. But to date, scientists have wondered how many organisms on our planet could develop radio-resistance, which is naturally protected from solar radiation by its magnetic field. While some scientists suggest that radio-resistance may develop along with other types of resistance, such as resistance to deciduousness, the question remains: which genes are particularly involved in radio-resistance?

To address this question, Dr. X’s team at the University of Wisconsin-Madison decided to “let the cells tell them.” Researchers started with naturally occurring non-resistant bacteria, E. coli and exposed it to repeated cycles of high-level irradiation. After exposure to radiation and several rounds of growth, a few radio-resistant populations emerged. Using a complete genome sequence, the researchers studied the genetic changes present in each radio-resistant population and determined which mutations provided radio-resistance to the bacteria.

In his first study, Dr. Cox’s team e. E. coli began to be exposed in 50 rounds of ionization (Brookbauer et al 2019b). After about 10 rounds, some radio-resistant populations emerged, and after 50, in a study of their genetic profile, three mutations responsible for radio-resistance were released, which are present in all genes linked to DNA repair mechanisms. Here, in their new study, the team exposed the bacteria to radiation exposure and 50 more rounds of selection.

Results published in Frontiers in Microbiology Show that the population of radioactive E. coli continued to grow and sub-populations emerged. Surprisingly, while the radio-resistance induced by the first series of ionization may be associated primarily with three mutations, the second may induce hundreds of mutations, including large carcinomas and duplication of some genes. “The four populations we are developing in this new trial have now reached levels of radio-resistance that are approaching the levels observed with Danococcus radiodurans. As the current trial progresses, genomic change is proving to be more complex than expected. Has happened. ” D Co. Says Cox.

Although it is difficult to pinpoint all the mutations that contribute to the increase in radio-resistance at this time, researchers have shown that more cellular metabolism is affected (ATP synthesis, iron-sulfur cluster biogenesis, cadaverine synthesis, and reactive oxygen oxygenation). Moreover, this study proves that radio-resistance Danococcus can develop at the level of radioiodurus, independently up to dissection-resistance. As radiation and experimental evolution continue to demonstrate, more information is being gathered about how to induce radio-resistance in bacteria. This one-day engineer can create a valuable toolbox of transformation of radiorestive probiotics, for example patients undergoing radiotherapy treatment, or astronauts who come to space for help.