Comprehensive investigation of Chernobyl bacteria reveals signs of adaptation to radiation

The most comprehensive study to date on microbial communities of the Chernobyl exclusion zone (Ukraine) revealed a great diversity of bacteria and some signs of its adaptation to the radiation released after the nuclear accident. This is what indicates an investigation carried out by the University of Oviedo and in which the Doñana-CSIC Biological Station and Brown University (USA) participate.

The study, which has just been published in environment pollution, found the same values ​​of diversity and richness of microorganisms in the wetlands sampled inside and outside the exclusion zone. The work also detected several bacteria that are more abundant in areas with high levels of radiationwhich indicates its high adaptability.

Germán Orizaola, researcher at the Department of Biología de Organismos y Sistemas at the University of Oviedo, recalls that 37 years have just passed since accident in reactor number 4 of the Chernobyl nuclear power plant, which caused the greatest release of radioactive substances into the environment of history.

“Several studies have analyzed the impact of the accident on nature and the renaturalization processes that are currently taking place in the area affected by the accident. radioactive contamination”, explains Orizaola.

“However, few studies have analyzed the situation of microbial communities, despite their crucial role in maintaining ecosystem functions due to its implication in the retention and release of carbon and the main soil nutrients”, he adds.

In and out of the exclusion zone

Fieldwork for this study was carried out in spring 2019 in different areas of northern Ukraine, both inside and outside the country. Chernobyl exclusion zone. A total of 21 wetlands were visited in which samples of water, sediments from the lagoons and the surrounding soil were collected for analyze the composition of microbial communities of the three environments.

These locations are distributed along a radiation gradient of more than three orders of magnitude, from areas with basal radiation levels (non-contaminated), such as areas that suffered the highest radiation doses at the time of the accident. Once in the laboratory, metagenomic and bioinformatics analyzes were used to characterize the composition and diversity of the microorganism communities in each locality.

The study found more than 20,000 different taxa of microorganisms at the sites examined. Analyzes have shown that Chernobyl wetlands support rich and diverse microbial communities three decades after the accident.

“The richness and diversity of microbial communities in sediments, soil and water were similar among the sampled wetlands. inside and outside the exclusion zoneand these parameters were not affected by the different levels of radiation”, points out the researcher.

Differences associated with radiation

The composition of the microbial communities showed some differences in their composition associated with radiation, as some groups of bacteria were especially abundant in areas with the highest levels of radiation.

“These microorganisms corresponded mainly to bacteria common in radioactive environments (uranium mines, nuclear waste deposits…); are capable of reduce uranium and other metalsand suggest the existence of patterns of adaptation to radiation at the community level in microorganisms in the area”, says Orizaola.

These results agree with previous studies that reveal that the Chernobyl exclusion zone currently maintains fully functional ecosystems and that shelter a great diversity of organisms, from the great endangered fauna (bears, lynxes, wolves…) to rich communities of bacteria, showing in some cases signs that suggest adaptation to radioactive environments.

“The study of the ecosystems in the areas affected by the nuclear accident is essential for a correct assessment of the environmental impact of the accident and to design response measures for potential future accidents. In addition, it provides important information to understand renaturation processes of the area”, concludes the researcher.