title: Physiological responses of the halophilic archaeon Halobacterium sp. strain NRC1 to desiccation and gamma irradiation.
abstract: We report that the halophilic archaeon Halobacterium sp. strain NRC-1 is highly resistant to desiccation, high vacuum and 60Co gamma irradiation. Halobacterium sp. was able to repair extensive double strand DNA breaks (DSBs) in its genomic DNA, produced both by desiccation and by gamma irradiation, within hours of damage induction. We propose that resistance to high vacuum and 60Co gamma irradiation is a consequence of its adaptation to desiccating conditions. Gamma resistance in Halobacterium sp. was dependent on growth stage with cultures in earlier stages exhibiting higher resistance. Membrane pigments, specifically bacterioruberin, offered protection against cellular damages induced by high doses (5 kGy) of gamma irradiation. High-salt conditions were found to create a protective environment against gamma irradiation in vivo by comparing the amount of DSBs induced by ionizing radiation in the chromosomal DNA of Halobacterium sp. to that of the more radiation-sensitive Escherichia coli that grows in lower-salt conditions. No inducible response was observed after exposing Halobacterium sp. to a nonlethal dose (0.5 kGy) of gamma ray and subsequently exposing the cells to either a high dose (5 kGy) of gamma ray or desiccating conditions. We find that the hypersaline environment in which Halobacterium sp. flourishes is a fundamental factor for its resistance to desiccation, damaging radiation and high vacuum.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, 3221 H.J. Patterson Hall, College Park, MD 20742, USA.
authors.forename: Molly
authors.initials: M
authors.lastname: Kottemann
authors.forename: Adrienne
authors.initials: A
authors.lastname: Kish
authors.forename: Chika
authors.initials: C
authors.lastname: Iloanusi
authors.forename: Sarah
authors.initials: S
authors.lastname: Bjork
authors.forename: Jocelyne
authors.initials: J
authors.lastname: DiRuggiero
mesh_terms: D003037:Cobalt Radioisotopes; D004249:DNA Damage / Q000528:radiation effects; D003890:Desiccation; D005720:Gamma Rays; D006217:Halobacterium / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D006358:Hot Temperature
chemical_list: D003037:Cobalt Radioisotopes