Sunlight-Exposed Biofilm Microbial Communities Are Naturally Resistant to Chernobyl Ionizing-Radiation Levels

BACKGROUND: The Chernobyl accident represents a long-term experiment on the effects of exposure to ionizing radiation at the ecosystem level. Though studies of these effects on plants and animals are abundant, the study of how Chernobyl radiation levels affect prokaryotic and eukaryotic microbial communities is practically non-existent, except for a few reports on human pathogens or soil microorganisms. Environments enduring extreme desiccation and UV radiation, such as sunlight exposed biofilms could in principle select for organisms highly resistant to ionizing radiation as well. METHODOLOGY/PRINCIPAL FINDINGS: To test this hypothesis, we explored the diversity of microorganisms belonging to the three domains of life by cultivation-independent approaches in biofilms developing on concrete walls or pillars in the Chernobyl area exposed to different levels of radiation, and we compared them with a similar biofilm from a non-irradiated site in Northern Ireland. Actinobacteria, Alphaproteobacteria, Bacteroidetes, Acidobacteria and Deinococcales were the most consistently detected bacterial groups, whereas green algae (Chlorophyta) and ascomycete fungi (Ascomycota) dominated within the eukaryotes. Close relatives to the most radio-resistant organisms known, including Rubrobacter species, Deinococcales and melanized ascomycete fungi were always detected. The diversity of bacteria and eukaryotes found in the most highly irradiated samples was comparable to that of less irradiated Chernobyl sites and Northern Ireland. However, the study of mutation frequencies in non-coding ITS regions versus SSU rRNA genes in members of a same actinobacterial operational taxonomic unit (OTU) present in Chernobyl samples and Northern Ireland showed a positive correlation between increased radiation and mutation rates. CONCLUSIONS/SIGNIFICANCE: Our results show that biofilm microbial communities in the most irradiated samples are comparable to non-irradiated samples in terms of general diversity patterns, despite increased mutation levels at the single-OTU level. Therefore, biofilm communities growing in sunlight exposed substrates are capable of coping with increased mutation rates and appear pre-adapted to levels of ionizing radiation in Chernobyl due to their natural adaptation to periodical desiccation and ambient UV radiation

Effects of Radioactive Contamination on Plant Populations: a Case of Low Doses and Multipollutant Exposure

An assessment of the state of plant and animal populations inhabiting polluted territories and the analysis of mechanisms of their adaptation to adverse environmental conditions undoubtedly has general biological importance. Consequently, studies that examine biological effects on non-human biota in natural settings provide a unique opportunity for obtaining information about the potential biological hazard associated with radioactive contamination. Nevertheless, up to now there is a distinct lack of quantitative data on the real long-term biological consequences of chronic radiation exposure lasting a long period of time. Actually, few studies exist that are directly relevant to understanding the responses of plant and animal populations to radionuclides in their natural environments. The results of long-term field experiments in the 30-km Chernobyl NPP zone, in the vicinity of the radioactive wastes storage facility (Leningrad Region), at radium production industry storage cell territory (the Komi Republic), in the Bryansk Region affected by the Chernobyl accident, and in Semipalatinsk Test Site, Kazakhstan that have been carried out in our laboratory on different species of wild and agricultural plants are discussed. Although radionuclides cause primary damage at the molecular level, there are emergent effects at the level of populations, non-predictable solely from the knowledge of elementary mechanisms of the pollutants influence. Plant populations growing in areas with relatively low levels of pollution are characterized by the increased level of both cytogenetic disturbances and genetic diversity. Man-made pollution may influence an evolution of exposed populations through a contaminant-induced selection process. Radioactive contamination of the plants environment activates genetic mechanisms, changing a populations resistance to exposure. However, in different radioecological situations, genetic adaptation to extreme edaphic conditions in plant populations could be achieved with different rates. These processes have a genetic basis; therefore, understanding changes at the genetic level should help in identifying more complex changes at higher levels

A Pipeline for Non-model Organisms for de novo Transcriptome Assembly, Annotation, and Gene Ontology Analysis Using Open Tools: Case Study with Scots Pine

RNA sequencing (RNA-seq) has opened up the possibility of studying virtually any organism at the whole transcriptome level. Nevertheless, the absence of a sequenced and accurately annotated reference genome may be an obstacle for applying this technique to non-model organisms, especially for those with a complex genome. While de novo transcriptome assembly can circumvent this problem, it is often computationally demanding. Furthermore, the transcriptome annotation and Gene Ontology enrichment analysis without an automatized system is often a laborious task. Here we describe step-by-step the pipeline that was used to perform the transcriptome assembly, annotation, and Gene Ontology analysis of Scots pine (Pinus sylvestris), a gymnosperm species with complex genome. Using only free software available for the scientific community and running on a standard personal computer, the pipeline intends to facilitate transcriptomic studies for non-model species, yet being flexible to be used with any organism

Genotoxicity and cytotoxicity assay of water sampled from natural reservoirs with contrast level of radioactive and chemical contamination

Comparative analysis of water from natural reservoirs located near a place of the underground nuclear explosion with rock outburst (Perm region) and the radium production industry storage cell (Komi Republic) with contrast levels of radioactive and chemical contamination was performed for the first time using bioindication and chemical analysis. Bioindication was carried out with anaphase-telophase chromosome aberration assay on A. schoenoprasum L. meristematic root tip cells. Even at very low levels of specific activity, both natural (238U, 232Th, 226Ra, 210Po, 210Pb) and artificial (90Sr, 137Cs, $^{230,240}$Pu) radionuclides contribute significantly (59-91 %) to an induction of genotoxic and toxic effects. The chemical factors strengthened or weakened the cytotoxicity effects and may modify a formation of certain type of chromosome disturbances. Our results clearly indicate that combined exposure to metal ions and radionuclides at levels officially adopted as permissible for humans may act synergistically and result in significant damage to different biota species.

Morphometric Measurements of Scots Pine Needles From Radioactively Contaminated Area

The morphometric indices of needles were investigated in chronically irradiated Scots pine (Pinus sylvestris L.) populations from territories that were heavily contaminated by radionuclides as a result of the Chernobyl Nuclear Power Plant accident. The variability in needle weight and length, as well as the fluctuating asymmetry indices were studied in seven contaminated and two reference populations of Scots pine in 2011, 2013, 2014 and 2016. The weight of needles in the contaminated populations was significantly higher than in the reference population; however, the dependence of this index on the level of radiation exposure was not revealed in the studied range of doses. The length of needles differed significantly from the references populations. The effect changed from decreasing to increasing in various years of observation; however, in 2016 this index decreased with the dose rate of β-radiation. The index of fluctuating asymmetry in needle length was significantly higher than at the reference sites during three years and correlated to the estimated annual absorbed dose in 2011 and 2013. No relationship was revealed between the asymmetry in weight of paired needles and radiation exposure

Cytogenetic variability in PInus sylvestris L. populations experiencing anthropogenic influence

Pinus sylvestris L. populations growing at the territory affected by nuclear waste storage facilities were monitored in 1997-2002. Cytogenetic damage levels within root meristem of seedlings significantly exceed corresponding controls. Populations experiencing man-caused influence have a higher seeds radioresistance and enlarged cytogenetic variance. These are considered as an indication of adaptation processes in the studied pine populations. An analysis of the structure of ecological-genetical variability is carried out. Changes of two components of the intrapopulational variance were studied in dependence on time and man-caused impact. The first component is engaged to the genetically determined variability of biological characteristics intrinsic for the species and is dominant in studied tree populations. The second is responsible for the variance originating from anthropogenic contamination of the natural habitat. A tendency of destabilizing dynamics and increasing mean values of intraclass correlation coefficient that is a measure of contribution from heterogeneity among trees into total cytogenetical variability is demonstrated under conditions of chronicle technogenic impact on pine populations

Plants ecotoxicology. A case of low doses and multipollutant exposure

Results of laboratory, “green-house" and long-term field experiments carried out on different plant species (spring barley, Scots pine, bulb onion and others) to study ecotoxical effects of low doses and concentrations of such common environmental factors as acute and chronic g-radiation, heavy metals, pesticides, artificial and heavy natural radionuclides, are presented. Special attention is paid to ecotoxic effects of chronic low dose exposures, synergistic and antagonistic effects of different factors' combined action. The results of long-term field experiments in the 30-km Chernobyl NPP zone and in the vicinity of a radioactive wastes storage facility are discussed. The data presented suggest that the further evolution of investigations in this field would issue in the development of a theoretical bases and practical procedures for environmental protection against radioactivity, taking into account the new experimentally confirmed facts about the presence of such essentially important singularities as the nonlinearity of a dose-effect relationship, radiation-induced genomic instability, phenomenon of radioadaptation, increased probability of synergetic and antagonistic effects of the combined action of different nature factors