Across the tree of life, radiation resistance is governed by antioxidant Mn2+, gauged by paramagnetic resonance

Ajay Sharma, Elena K. Gaidamakova, Olga Grichenko, Vera Y. Matrosova, Veronika Hoeke, Polina Klimenkova, Isabel H. Conze, Robert P. Volpe, Rok Tkavc, Cene Gostinčar, Nina Gunde-Cimerman, Jocelyne DiRuggiero, Igor Shuryak, Andrew Ozarowski, Brian M. Hoffman*, Michael J. Daly

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


Despite concerted functional genomic efforts to understand the complex phenotype of ionizing radiation (IR) resistance, a genome sequence cannot predict whether a cell is IR-resistant or not. Instead, we report that absorption-display electron paramagnetic resonance (EPR) spectroscopy of nonirradiated cells is highly diagnostic of IR survival and repair efficiency of DNA double-strand breaks (DSBs) caused by exposure to gamma radiation across archaea, bacteria, and eukaryotes, including fungi and human cells. IR-resistant cells, which are efficient at DSB repair, contain a high cellular content of manganous ions (Mn2+) in high-symmetry (H) antioxidant complexes with small metabolites (e.g., orthophosphate, peptides), which exhibit narrow EPR signals (small zero-field splitting). In contrast, Mn2+ ions in IR-sensitive cells, which are inefficient at DSB repair, exist largely as low-symmetry (L) complexes with substantially broadened spectra seen with enzymes and strongly chelating ligands. The fraction of cellular Mn2+ present as H-complexes (H-Mn2+), as measured by EPR of live, nonirradiated Mn-replete cells, is now the strongest known gauge of biological IR resistance between and within organisms representing all three domains of life: Antioxidant H-Mn2+ complexes, not antioxidant enzymes (e.g., Mn superoxide dismutase), govern IR survival. As the pool of intracellular metabolites needed to form H-Mn2+ complexes depends on the nutritional status of the cell, we conclude that IR resistance is predominantly a metabolic phenomenon. In a cross-kingdom analysis, the vast differences in taxonomic classification, genome size, and radioresistance between cell types studied here support that IR resistance is not controlled by the repertoire of DNA repair and antioxidant enzymes.

Original languageEnglish (US)
Pages (from-to)E9253-E9260
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number44
StatePublished - Oct 31 2017


  • DNA repair
  • DSB
  • Deinococcus
  • EPR
  • Ionizing radiation

ASJC Scopus subject areas

  • General


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