Low environmental radiation background impairs biological defence of the yeast Saccharomyces cerevisiae to chemical radiomimetic agents

The REPAIR Project: Examining the Biological Impacts of Sub-Background Radiation Exposure within SNOLAB, a Deep Underground Laboratory

“…When grown in a sub-background environment, cultured cells showed an increase in basal levels of DNA damage and mutation rate (13)(14)(15). Low-background-adapted cells were also found to be more sensitive to induced genetic damage after exposure to a high-dose radiation challenge (15)(16)(17)(18) or chemical agent (13,16,19). This increased sensitivity was correlated to a reduction in free radical scavenging ability (13,15,16,18).…”

“…Lake whitefish develop slowly, close to 200 days depending on temperature (36,37). This is important since, in many of the previous sub-background experiments, effects were observed only after prolonged incubation (10,13,14,17,(19)(20)(21). Lastly, embryos can be easily staged and quantified for growth rate (38), which is one of the main end points examined in past studies.…”

“…This increased sensitivity was correlated to a reduction in free radical scavenging ability (13,15,16,18). In many cases, changes in repair capacity or growth rate were only observed after prolonged incubation in a sub-background environment on the order of weeks to months (10,13,14,17,(19)(20)(21).…”

Below-Background Ionizing Radiation as an Environmental Cue for Bacteria

“…The first evidence of a deleterious biological response to radiation doses lower than background was reported by Planel et al (1987), who observed a longer generation time in Paramecium tetraurelia and a lower cell number in Synechococcus lividus cultures when these organisms were grown shielded from radiation at dose rates 17 and 6 times lower than background, respectively. Since then, experiments with other organisms have shown similar deleterious effects when exposed to below background levels of radiation, such as lower protection to mutational damage in Saccharomyces cerevisiae (Satta et al, 1995); higher sensitivity to apoptosis, higher intracellular concentration of oxidative stressrelated enzymes, and higher mutation rate induced by gamma rays (after conditioning under below background conditions) in Cricetulus griseus (Satta et al, 2002); growth rate retardation in Mus musculus L5178Y cells (Kawanishi et al, 2012), changes in the concentration of oxidative stress-related enzymes (Fratini et al, 2015), and lower cell number and/or up regulation of DNA repair and oxidative stress genes in Shewanella oneidensis and Deinococcus radiodurans (Smith et al, 2011;Castillo et al, 2015).…”

“…However, using growth as the only endpoint to measure the effect of a particular environmental variable might be misleading since cells employ multiple physiological mechanisms in response to changing environments to maintain homeostasis. In order to circumvent this limitation, similar low-radiation dose experiments have used different approaches for a more indepth analysis of the cellular response, such as micronucleus assays (Carbone et al, 2009), enzymatic activity (Satta et al, 2002;Carbone et al, 2009;Fratini et al, 2015), mutation assays (Satta et al, 1995(Satta et al, , 2002Fratini et al, 2015), and differential gene expression (Castillo et al, 2015;Fratini et al, 2015). In the present study, we measured the expression of genes related to some of these types of stress, on cells collected at various time points in order to compare their differential expression.…”