Roles of DNA repair and membrane integrity in heat resistance of Deinococcus radiodurans
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SHORT COMMUNICATION
Roles of DNA repair and membrane integrity in heat resistance of Deinococcus radiodurans Anja Bauermeister • Claudia Hahn • Petra Rettberg • Gu¨nther Reitz • Ralf Moeller
Received: 10 June 2012 / Accepted: 17 July 2012 / Published online: 5 August 2012 Ó Springer-Verlag 2012
Abstract To study the effects of heat shock on Deinococcus radiodurans and the role of DNA repair in high temperature resistance, different strains of D. radiodurans (wild type, recA, irrE, and pprA) were treated with temperatures ranging from 40 to 100 °C under wet and dry conditions. The mutant strains were more sensitive to wet heat of C60 °C and dry heat of C80 °C than the wild type. Both wild-type and DNA repair-deficient strains were much more resistant to high temperatures when exposed in the dried state as opposed to cells in suspension. Molecular staining techniques with the wild-type strain revealed that cells in the dried state were able to retain membrane integrity after drying and subsequent heat exposure, while heat-exposed cells in suspension showed significant loss of membrane integrity and respiration activity. The results suggest that the repair of DNA damage (e.g., DNA doublestrand breaks by RecA and PprA) is essential after treatment with wet heat at temperatures [60 °C and dry heat [80 °C, and the ability of D. radiodurans to stabilize its plasma membrane during dehydration might represent one aspect in the protection of dried cells from heat-induced membrane damage.
Communicated by Erko Stackebrandt. A. Bauermeister C. Hahn P. Rettberg G. Reitz R. Moeller (&) Radiation Biology Department, Research Group ‘‘Astrobiology’’, Institute of Aerospace Medicine, German Aerospace Center (DLR), Linder Hoehe, 51147 Cologne, Germany e-mail: [email protected] C. Hahn Saarland University, 66123 Saarbru¨cken, Germany
Keywords Deinococcus radiodurans Heat resistance DNA damage Membrane lesions DNA repair mechanisms
Introduction Deinococcus radiodurans is well known for its extreme radiation resistance. Formerly called Micrococcus radiodurans, it was first isolated in 1956 from canned meat treated with 4,000 Gy of c-radiation (Anderson et al. 1956). It was soon revealed that D. radiodurans can not only tolerate surprisingly high doses of ionizing radiation (almost 1,000 times the lethal dose for humans), but is also extremely resistant to other environmental stress factors such as UV radiation, prolonged desiccation, oxidative stress, and genotoxic chemicals (Blasius et al. 2008; Battista 1997; Daly 2009). Both ionizing radiation and desiccation cause the DNA to shatter into small fragments, which are, however, reassembled almost error-free by D. radiodurans (Battista et al. 1999). It has been suggested that the extreme radiation resistance is a consequence of an adaptation to prolonged desiccation in this non-sporeforming soil bacterium (Mattimore and Battista 1996). Many studies have been undertaken to identify the key mechanisms underlying this phenotype, and now the picture is emerging that no s
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