Radiation response mechanisms of the extremely radioresistant bacterium Deinococcus radiodurans

Effect of microgravity on recovery of bacterial cells from radiation damage was examined in IML-2, S/MM-4 and S/MM-9 experiments using the extremely radioresistant bacterium Deinococcus radiodurans. The cells were irradiated with gamma rays before the space flight and incubated on board the Space Sh...

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Bibliographic Details
Published in:Uchū seibutsu kagaku 2004-11, Vol.18 (3), p.134-135
Main Authors: Kobayashi, Yasuhiko, Narumi, Issay, Satoh, Katsuya, Funayama, Tomoo, Kikuchi, Masahiro, Kitayama, Shigeru, Watanabe, Hiroshi
Format: Article
Language:English
Subjects:
Bacterial Proteins
Colony Count, Microbial
Cosmic Radiation
Deinococcus - genetics
Deinococcus - growth & development
Deinococcus - radiation effects
DNA Repair
DNA, Bacterial
Gamma Rays
Mutation
Radiation Tolerance
Space Flight
Space life sciences
Weightlessness
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Summary:Effect of microgravity on recovery of bacterial cells from radiation damage was examined in IML-2, S/MM-4 and S/MM-9 experiments using the extremely radioresistant bacterium Deinococcus radiodurans. The cells were irradiated with gamma rays before the space flight and incubated on board the Space Shuttle. The survival of the wild type cells incubated in space increased compared with the ground controls, suggesting that the recovery of this bacterium from radiation damage was enhanced under the space environment. No difference was observed between the survivals of radiosensitive mutant rec30 cells incubated in space and on the ground. The amount of DNA-repair related RecA protein induced under microgravity was similar to those of ground controls, however, induction of PprA protein, product of a unique radiation-inducible gene (designated pprA) responsible for loss of radiation resistance in repair-deficient mutant, KH311, was enhanced under microgravity compared with ground controls. Recent investigation in vitro showed that PprA preferentially bound to double-stranded DNA carrying strand breaks, inhibited Escherichia coli exonuclease III activity, and stimulated the DNA end-joining reaction catalyzed by DNA ligases. These results suggest that D. radiodurans has a radiation-induced non-homologous end-joining (NHEJ) repair mechanism in which PprA plays a critical role.
ISSN:0914-9201