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As you read this story, you will learn the following:
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As several reactors exploded, water seeping into the Fukushima Daiichi nuclear power plant merged with radioactive sludge and became highly irradiated.
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Ionizing radiation apparently didn’t prevent certain types of bacteria from multiplying in the water, but surprisingly, they weren’t the radiation-resistant types expected in such an environment.
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Because these bacteria also cause corrosion, they can provide valuable information on how to safely decommission nuclear reactors.
Japan shut down all its nuclear facilities after the 2011 tsunami caused a massive meltdown at the Fukushima Daiichi nuclear power plant. However, Japan recently restarted one of the surviving reactors at Fukushima, but it was not the only one to survive the disaster.
During the decommissioning of the Fukushima nuclear power plant, water seeped into radioactive waste remaining inside the reactor buildings. Soon, an environment considered uninhabitable is actually crawling with microorganisms. Microorganisms can be a major obstacle in the cleanup process after decommissioning nuclear power plants, as many microorganisms can corrode metal, and microbial colonies can cloud water and reduce visibility.
Recently, biologists Tomoro Warashina and Akio Kanai of Keio University in Tokyo made extraordinary discoveries while analyzing microbial samples collected from highly radioactive water in a power plant donut beneath the reactor building. Bacteria with no specific genetic resistance to the harmful effects of radiation thrive in the sludge. In the face of a nuclear disaster, organisms must either perish or evolve. Mutations made it possible for everything from wolves to nearly indestructible black mold to thrive in Chernobyl’s otherwise hostile environment decades later. This is why scientists expect to find radio-resistant microbial species, e.g. Deinococcus radiodurans or Methylobacterium radiodurans in their sample.
As the team explained in a recently published study Applied and Environmental MicrobiologyThe microbiome they analyzed has been exposed to sustained radiation, and gathering information about such microorganisms is critical to understanding how to sustainably treat stagnant radioactive water environments during decommissioning efforts. “Certain microorganisms are known to have mechanisms to resist high levels of ionizing radiation,” they wrote.
After testing the genetic markers of different microorganisms in the water samples, Warashina and Kanai found that the water samples were filled with bacteria from Biobacterium and Brevibacterium genus. These chemotrophic bacteria survive by oxidizing inorganic compounds such as manganese or sulfide. Sulfur oxidizers benefit from sulfite oxidase, an enzyme secreted by mitochondria that detoxifies sulfides by breaking down sulfur-containing amino acids. They convert sulfides into harmless sulfates. Scientists also discovered small amounts of iron oxidizers Heflea and sheath fixation A genus that survives by converting one form of iron into another.
None of the species discovered by Kanai and Tongke have strong radiation resistance. However, these bacteria are still able to thrive despite high levels of ionizing radiation being toxic to many other life forms. The question is, how? The study’s authors observed that a mixture of emergency cooling water and seawater within the torus chamber appeared to support the growth of biofilms on metal surfaces. Metals are often oxidized and corroded by these bacteria, and scientists theorized that the slime covering these bacterial clumps may actually provide them with additional protection from radiation. The team also analyzed microbial communities to see which ones were causing the most corrosion and therefore needed to be targeted to prevent further breakdown of the metal during decommissioning.
“The extremely low proportion of bacterial genera known to be radioresistant suggests that radioactivity has little impact on selection in the torus chamber water,” they said. “In contrast, [most] Bacterial genera in annulus water are associated with metal corrosion, indicating that the impact of bacteria on metal corrosion must be considered in long-term decommissioning efforts. “
Another thing that piqued the team’s interest is that many of the microorganisms found in the donut chamber also thrive in the ocean. The bacteria may have been swept in by tsunami waves, or their adaptations to the marine environment may have helped them survive inside the abandoned nuclear reactors. Life, well, always finds a way.
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