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Here’s what you’ll learn when you read this story:
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Since several of its reactors exploded, the water that seeped into the Fukushima Daiichi nuclear power plant merged with radioactive sludge and became heavily irradiated.
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Ionizing radiation apparently did not prevent some types of bacteria from multiplying in the water, but surprisingly, they are not the radiation-resistant types expected in an environment like this.
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Because these bacteria also cause corrosion, they can provide valuable information on how to safely decommission nuclear reactors.
Following the 2011 tsunami that caused massive meltdowns at the Fukushima Daiichi Nuclear Power Plant, Japan shut down all its nuclear operations. However, Japan recently restarted one of Fukushima’s surviving reactors — but that reactor wasn’t the only thing that survived the disaster.
During the time the Fukushima plant was abandoned, water seeped into the radioactive waste that remained in the reactor buildings. Soon, an environment that was supposed to be uninhabited was actually teeming with microbes. Microbes can be a major obstacle during the cleanup that comes with decommissioning nuclear power plants, as many species corrode metal, and swarms can transform water and reduce visibility.
Recently, biologists Tomoro Warashina and Akio Kanai of Keio University in Tokyo made an extraordinary discovery when they analyzed samples of microbes taken from the highly radioactive water inside the power plant’s torus chamber, beneath the reactor building. Bacteria with no special genetic resistance to the harmful effects of radiation thrived in the sludge. In the face of a nuclear disaster, organisms either perish or evolve. The mutations made it possible for everything from wolves to a nearly indestructible black mold to thrive in the otherwise hostile environment of Chernobyl even decades later. This is why scientists expected to find radiation-resistant microbial species such as Deinococcus radiodurans or Methylobacterium radiotolerant in their samples.
As the team explained in a study recently published in Applied and Environmental Microbiologythe microbiome they analyzed was exposed to persistent radiation, and gathering information about such microorganisms is vital to understanding how to sustainably treat radioactive, stagnant water environments during decommissioning. “Certain microorganisms are known to have mechanisms that confer resistance to high levels of ionizing radiation,” they wrote.
After testing their water samples for genetic markers of different microbes, Warashina and Kanai discovered that it was full of bacteria from Limnobacter and Brevirhabdus the genders. These chemolithotrophic bacteria live by oxidizing inorganic compounds such as manganese or sulfides. Sulfur oxidizers benefit from the enzyme sulfite oxidase, which is secreted by their mitochondria and detoxifies sulfides by breaking down sulfur-containing amino acids. They convert sulfides into harmless sulfates. Scientists also found a lower amount of iron oxidants from Hoeflea and Sphinopyxis genera, which live by transforming one form of iron into another.
None of the species found by Kanai and Warashina have radiation resistance superpowers. However, despite high levels of ionizing radiation that would have been toxic to many other life forms, these bacteria were able to thrive. The question is, how? The study authors observed that the mixture of emergency cooling water and seawater inside the torus chamber appeared to support the growth of biofilms on the metal surfaces. Metals are commonly oxidized and corroded by these bacteria, and the scientists reasoned that it is possible that the slime covering such bacterial masses may have actually provided them with additional protection against radiation. The research team also looked at microbial communities to see which caused the most corrosion and therefore should be targeted to prevent further metal breakdown during the decommissioning process.
“The proportions of bacterial genera known to be radiation resistant were extremely low, suggesting that the impact of radioactivity on selection in the water in the torus chamber was minimal,” they said. “In contrast, [most] of the bacterial genera in the torus chamber water were associated with metal corrosion, indicating that the impact of bacteria on metal corrosion needs to be considered in long-term decommissioning work.”
Another thing that caught the team’s interest was that many of the microbes found in the torus chamber also thrive in the ocean. It’s possible that these bacteria collapse with the tsunami waves, or that something about their adaptations to a marine environment also helps them stay alive in the bowels of a dead nuclear reactor. Life, uh, finds a way.
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