Exposure of Deinococcus radiodurans to both static magnetic fields and gamma radiation: observation of cell recuperation
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Exposure of Deinococcus radiodurans to both static magnetic fields and gamma radiation: observation of cell recuperation effects Henriette Righi 1,2 & João D. T. Arruda-Neto 1 & José G. C. Gomez 2 & Luiziana F. da Silva 2 & Elizabeth S. R. Somessari 3 & Aline C. C. Lemos 2 Received: 6 March 2020 / Accepted: 4 August 2020 / Published online: 18 August 2020 # Springer Nature B.V. 2020
Abstract
The extremophilic bacterium Deinococcus radiodurans displays an extraordinary ability to withstand lethal radiation effects, due to its complex mechanisms for both proteome radiation protection and DNA repair. Published results obtained recently at this laboratory show that D. radiodurans submitted to ionizing radiation results in its DNA being shattered into small fragments which, when exposed to a “static electric field’ (SEF), greatly decreases cell viability. These findings motivated the performing of D. radiodurans exposed to gamma radiation, yet exposed to a different exogenous physical agent, “static magnetic fields” (SMF). Cells of D. radiodurans [strain D.r. GY 9613 (R1)] in the exponential phase were submitted to 60Co gamma radiation from a gamma cell. Samples were exposed to doses in the interval 0.5– 12.5 kGy, while the control samples were kept next to the irradiation setup. Exposures to SMF were carried out with intensities of 0.08 T and 0.8 T delivered by two settings: (a) a device built up at this laboratory with niobium magnets, delivering 0.08 T, and (b) an electromagnet (Walker Scientific) generating static magnetic fields with intensities from 0.1 to 0.8 T. All samples were placed in a bacteriological incubator at 30 °C for 48 h, and after incubation, a counting of colony forming units was performed. Two sets of cell surviving data were measured, each in triplicate, obtained in independent experiments. A remarkable similarity between the two data sets is revealed, underscoring reproducibility within the 5% range. Appraisal of raw data shows that exposure of irradiated cells to SMF substantially increases their viability. Data interpretation strongly suggests that the increase of D. radiodurans cell viability is a sole magnetic physical effect, driven by a stochastic process, improving the efficiency of the rejoining of DNA fragments, thus increasing cell viability. A type of cut-off dose is identified at 10 kGy, above which the irradiated cellular system loses recovery and the cell survival mechanism collapses. Keywords Deinococcus radiodurans . Gamma radiation . Surviving curves . Static magnetic fields . DNA shattered fragments . Cell recuperation effects
* João D. T. Arruda-Neto [email protected] Extended author information available on the last page of the article
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1 Introduction The extremophilic bacterium Deinococcus radiodurans has been a biomodel high on the agenda of cellular and molecular biologists, mostly due to its intriguing and complex mechanisms for both proteome radiation protection and DNA repair, following exposure to high doses of ionizing radiations [1–3]. It is a
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