Radiation resistance in thermophiles: mechanisms and applications

Abstract

The study of prokaryotic life in high temperature environments viz., geothermal areas, hot, acidic geysers and undersea hydrothermal vents has revealed the existence of thermophiles (or hyperthermophiles). These microorganisms possess various stress adaptation mechanisms which enable them to bypass multiple physical and chemical barriers for survival. The discovery of radiation resistant thermophile Deinococcus geothermalis has given new insights into the field of radiation microbiology. The ability of radiation resistant thermophiles to deal with the lethal effects of ionizing radiations like DNA damage, oxidative bursts and protein damage has made them a model system for exobiology and interplanetary transmission of life. They might be an antiquity of historical transport process that brought microbial life on Earth. These radiation resistant thermophiles are resistant to desiccation as well and maintain their homeostasis by advance DNA repair mechanisms, reactive oxygen species (ROS) detoxification system and accumulation of compatible solutes. Moreover, engineered radioresistant thermophilic strains are the best candidate for bioremediation of radionuclide waste while the extremolytes produced by these organisms may have predicted therapeutic uses. So, the present article delineate a picture of radiation resistance thermophiles, their adaptive mechanisms to evade stress viz., radiation and desiccation, their present applications along with new horizons in near future.

DNA damage response signaling pathways and targets for radiotherapy sensitization in cancer

“…However, radiotherapy is typically accompanied by the unavoidable development of cancer cell resistance to radiation exposure 35,36 . Radiotherapy resistance (RR), defined as a reduction in the effectiveness of antitumor therapy 37 , is a major obstacle in cancer treatment.…”

Earth's Stratosphere and Microbial Life

“…These can typically survive acute exposures to ionizing radiation ≥12,000 Gy (with D. radiodurans having survived up to 20,000 Gy; Krisko and Radman, 2013), compared to 8,000 Gy of γ-radiation survived by some fungi, while E. coli is killed by only 200-800 Gy (Harris et al, 2009). Deinococcus species are also resistant to desiccation by maintaining homeostasis using DNA repair mechanisms, ROS detoxification and accumulation of compatible solutes (Ranawat and Rawat, 2017). Recent stratospheric Deinococcus isolates include a radioresistant orange-pigmented, desiccation-tolerant, UV-and γradiation resistant bacterium Deinococcus aerius TR0125 (from 0.8-5.8 km), and Deinococcus aetherius ST0316 (from 10-12 km above Japan).…”

Remote oxidative modifications induced by oxygen free radicals modify T/R allosteric equilibrium of a hyperthermophilic lactate dehydrogenase

“…With respect to high temperature, the present-day habitats of (hyper) thermophilic microorganisms' mimics conditions encountered in primitive hot archaean oceans (Nisbet and Sleep, 2001). At the cellular level, numerous studies show that thermophilic organisms are capable to resist strong doses of ionizing radiation (IR) (Ranawat and Rawat, 2017). When exposed to IR, cells are damaged by direct and indirect effects.…”

“…Most of the damages are indirect and are induced by water radiolysis, which produces reactive oxygen species (ROS). The capacity of cells to thrive in strong IR environment was analyzed to be the consequence of important DNA repair capacity, ROS detoxification mechanisms and accumulation of protective solute such as trehalose (Ranawat and Rawat, 2017). In contrast, the putative favorable relationship between thermal stability of cell macromolecules (in particular proteins) and resistance to oxidative stress resulting from irradiation is not documented.…”