Living and thriving beneath Fukushima’s dead reactors is something strange

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Here’s what you’ll learn as you read this story:

• After several of its reactors exploded, water entering the Fukushima Daiichi nuclear power plant mixed with radioactive sludge and became highly irradiated.

• Ionizing radiation did not prevent some types of bacteria from reproducing in the water, but surprisingly, they were not the radiation-resistant types expected in this type of environment.

• Because these bacteria also cause corrosion, they can provide valuable information on how to safely decommission nuclear reactors.

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Following the 2011 tsunami and the massive meltdown at the Fukushima Daiichi nuclear power station, Japan shut down all its nuclear operations. Recently, however, Japan restarted one of Fukushima’s surviving reactors — but that reactor wasn’t the only survivor of the disaster.

During the Fukushima plant’s abandonment, water fell into the radioactive waste that remained in the reactor buildings. Soon, an environment thought to be uninhabitable was actually crawling with microbes. Microorganisms can be a major obstacle during cleanup during decommissioning of nuclear power plants, as many species corrode metal, and their swarms can cloud water and reduce visibility.

Recently, biologists Tomoro Warashina and Akio Kanai of Keio University in Tokyo made an extraordinary discovery while analyzing samples of microbes taken from highly radioactive water inside the power plant’s torus room below the reactor building. Bacteria with no special genetic resistance to the harmful effects of radiation were thriving in the sludge. When faced with a nuclear disaster, organisms either perish or evolve. Mutations have made it possible for everything from wolves to nearly indestructible black mold to thrive decades later in Chernobyl’s otherwise hostile environment. Scientists therefore expect to find radiation-resistant microbial species Deinococcus radiodurans or Methylobacterium radiotolerans in their specimens.

The team clarified in a recently published study Applied and Environmental MicrobiologyThe microbiome they analyzed was continuously exposed to radiation, and gathering information about such microbes is vital to understanding how to sustainably treat a stagnant, radioactive water environment during decommissioning operations. “Some microorganisms are known to have mechanisms to resist high levels of ionizing radiation,” they wrote.

After testing their water samples for genetic markers of various bacteria, Warashina and Kanai discovered that it was teeming with bacteria. Limnobacter and Brevirhabdus genera. These chemolithotrophic bacteria make their living by oxidizing inorganic compounds such as manganese or sulfide. Sulfur oxidizers benefit from the sulfite oxidase enzyme, which is secreted by their mitochondria and detoxifies sulfides by breaking down sulfur-containing amino acids. They convert sulfides into harmful sulfates. Scientists also found small amounts of iron oxidizers Hoeflea and Sphinopyxes Genera, which live by converting one form of iron into another.

None of the species Kanai and Warashina have superpowers for radiation resistance. However, despite high levels of ionizing radiation that would have been toxic to many other forms of life, these bacteria were able to thrive. The question is, how? The authors of the study observed that the mixture of emergency cooling water and seawater inside the torus room appeared to support the growth of biofilms on the metal surfaces. Metals are usually oxidized and corroded by these bacteria, and the scientists reasoned that the slime covering such bacterial masses may actually have given them additional protection from radiation. The research team also analyzed microbial communities to determine which ones cause the most corrosion and therefore need to be targeted to prevent further breakdown of the metals during the decommissioning process.

“The proportion of bacterial genera known to be radioresistant was very low, suggesting that the effect of radioactivity on selection within the torus chamber water was minimal,” they said. “On the contrary, [most] Bacterial genera in torus room water were associated with metal corrosion, indicating that the effect of bacteria on metal corrosion should be considered in long-term decommissioning operations.”

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 is possible that these bacteria collided with tsunami waves or that something about their adaptation to the marine environment helped them survive in the bowels of a dead nuclear reactor. Life, uh, finds a way.

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