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.

Extremely Radiation-Resistant Mutants of a Halophilic Archaeon with Increased Single-Stranded DNA-Binding Protein (RPA) Gene Expression

“…NRC-1 has recently been shown to have high resistance to ␥ radiation (20). The resistance was attributed to the ability to repair double-strand breaks as well as to the protective properties of specific membrane pigments to oxidative damage.…”

Resistance of extremely halophilic archaea to zinc and zinc oxide nanoparticles

“…They are also reported to have survived approximately 250 millions of years by getting entrapped in salt crystals (Legat et al 2013;Schubert et al 2010;Bragança and Furtado 2009). They are polyextremophilic surviving extreme conditions such as high salinity, high temperatures, neutral to alkaline pH, low water activity (a w ), and extreme gamma radiations (Kottemann et al 2005). Studies on Zn resistance in halophilic archaea are scarce.…”

New insights into microbial adaptation to extreme saline environments

“…Halophilic microbes thrive in nearly saturated brines. They are remarkably tolerant to multiple stresses such as desiccation, temperature, toxic metals, radiation etc (28)(29)(30)(31)(32). Halophilic strains have even been shown to survive space conditions (33,34).…”