The Chernobyl Exclusion Zone has been largely untouched by humans since the Chernobyl nuclear explosion in 1986. Now over 30 years later, there’s been an abundance of wildlife in the 1,600 square mile zone despite their exposure to radioactive material in the soil and food. Scientists are monitoring animal populations with camera traps set up in this area which have captured an abundance of wildlife on these cameras: grey wolves, raccoon dogs, boars, and foxes.
What goes on beneath the surface, what’s happening within these animals or within the soils and plants, is a question that these camera traps can’t answer. There could be genetic damage and higher mutation rates in the animal itself. And, their microbiomes of these environments must have also changed in some way.
The gut microbiome of the bank vole
One of these animals is the bank vole. A team of scientists led by Anton Lavrinienko from the University of Oulu sequenced the gut microbiome of bank voles in contaminated and uncontaminated areas near Chernobyl. They found that the ratio between Firmicutes and Bacteroidetes bacteria shifted. The number of Firmicutes compared to Bacteroidetes in the vole gut doubled high radiation areas.
This change could reflect environmental changes in high radiation areas. Gut communities dominated by Bacteroidetes digest diverse foods includes leaves, seeds, and insects. On the other hand, Firmicutes tend to digest otherwise indigestible starches and plant cell wall glycans. The increase in the Firmicutes:Bacteroidetes ratio could indicate a reduced arthropod population or increased plant populations.
Aside from this, radiation-associated bacteria contained genes for different functions: pathways involved in degradation, assimilation of carbohydrates, xenobiotic biodegradation, and DNA repair.
The conclusion? Exposure to radionuclides alters the gut microbiome. In fact, the differences were distinct enough that the researchers were able to classify samples whether they came from high or low radiation sites based on the microbial community with over 90% accuracy.
Microbial communities in the trenches
Aside from the animal gut microbiota changes, the soil prokaryotic communities in Chernobyl were (not surprisingly) also affected. A different group of researchers from CNRS and other institutes in France found this out by examining soil microbial communities in the waste disposal trench T22. In trench T22, contaminated soil, vegetation, and debris from the Red Forest were buried. Pine trees are now reclaiming the area.
The team of researchers revealed the bacteria and archaea present both inside and near T22 by sequencing. In all samples, there was a high abundance of Chloroflexi and AD3, microorganisms commonly dominant in soil particularly from cold climates. These organisms were previously found to dominate soil microbial communities after acute gamma irradiation and detected in natural uranium and uranium-contaminated sites.
However, there were many phyla unique to trench soils: Crenarchaeota, Acidobacteria, AD3, Chloroflexi, Proteobacteria, Verrucomicrobia and WPS-2. Generally, the trenches were more diverse than the surrounding areas, likely enhanced by cellulosic waste burial in the soil.
As this article winds down, you might be wondering whether this study found the famous radiation resistant microbe, Deinococcus radiodurans, in the soil. It’s ambiguous. In the sequencing, they found that D. radiodurans sequences were just a very small portion of all the sequences, just 0.0004 – 0.084%. In follow up studies either by PCR or culturing the bacteria, they could not detect the bacterium. The microbe could either be present in small amounts of completely absent.
