Simulating the Impact of the Natural Radiation Background on Bacterial Systems: Implications for Very Low Radiation Biological Experiments

Abstract

At very low radiation dose rates, the effects of energy depositions in cells by ionizing radiation is best understood stochastically, as ionizing particles deposit energy along tracks separated by distances often much larger than the size of cells. We present a thorough analysis of the stochastic impact of the natural radiative background on cells, focusing our attention on E. coli grown as part of a long term evolution experiment in both underground and surface laboratories. The chance per day that a particle track interacts with a cell in the surface laboratory was found to be 6 × 10−5 day−1, 100 times less than the expected daily mutation rate for E. coli under our experimental conditions. In order for the chance cells are hit to approach the mutation rate, a gamma background dose rate of 20 μGy hr−1 is predicted to be required.

Transcriptome analysis reveals a stress response of Shewanella oneidensis deprived of background levels of ionizing radiation

“…oneidensis to retain homeostasis. Our hypothesis is in apparent contradiction to recently published modeling studies that suggest the improbability that the dose rates for our study could exert any effect on our cells to significantly alter their physiology [ 73 , 74 ]. However, the paradigm shift we present is that the genome-wide gene regulation response in our model is precisely due to a lower intracellular radiolysis products concentration because of a reduced hit rate by radiation tracks.…”

Understanding low radiation background biology through controlled evolution experiments

“…This was underlined by Katz (2016) and has been further explored in the context of underground laboratories by Lampe, Biron, et al (2016). These investigations show that radiation tracks from background sources on the order of 100 nGy/hr interact rarely with bacterial cells, affecting less than 0.1% of the population per day.…”

“…When organisms and radiation together are pictured as a bulk material, radio‐induced chemical species cannot account for the reductions in antioxidant abundancies observed, for example, in barn swallows (Møller, Surai, & Mousseau, ). The variations in antioxidant abundance in response to different radiation backgrounds may require more detail than a continuum model offers to be understood (this has been explored in part by Lampe, Biron, et al., ). At the level of a cell, radiation‐induced radicals are created stochastically, whenever radiation traverses the cell.…”

“…Many model organisms exist for which long-term controlled evolution data and protocols are already available, such as the prokaryote E. coli (Barrick et al, 2009;Lenski, Rose, Simpson, & Tadler, 1991), the eukaryote S. cerivasae (Ferea, Botstein, Brown, & Rosenzweig, 1999;Sonderegger & Sauer, 2003) and even the fruit fly Drosophila melanogaster (Burke et al, 2010). Advancing along this path, experiments are currently underway in the Modane Underground Laboratory to reproduce E. coli based long-term evolution experiments in different radiation environments (Lampe, Biron, et al, 2016). Through these pilot experiments, we hope to clarify the extent to which LB environments change the evolutionary comportment of a simple bacterial population.…”

Is bacterial luminescence response to low-dose radiation associated with mutagenicity?

“…A number of research findings indicate that low-intensive gamma irradiation might induce a mutagenic effect in different organisms (Bolsunovsky et al, 2016;Sykes et al, 2006;Hussain and Ehrenberg, 1979); however, estimated probability of direct interaction of gamma-rays with bacterial cells is very low (Lampe et al, 2016).…”