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Applied and Environmental Microbiology (1)
Life : Open Access Journal (1)
PLoS ONE (1)
Leuko, Stefan (3)
Arakawa, Kazuharu (1)
Burns, Brendan P. (1)
Cumbers, John (1)
Fendrihan, Sergiu (1)
Fujiyama, Asao (1)
Harnoto, Raechel (1)
Horikawa, Daiki D. (1)
Katayama, Toshiaki (1)
Kunieda, Takekazu (1)
Legat, Andrea (1)
Pontifex, Ashleigh L. (1)
Rettberg, Petra (1)
Rogoff, Dana (1)
Rothschild, Lynn J. (1)
Sakakibara, Iori (1)
Stan-Lotter, Helga (1)
Toyoda, Atsushi (1)
Year of Publication
On the Response of Halophilic Archaea to Space Conditions
Pontifex, Ashleigh L.
Burns, Brendan P.
Life : Open Access Journal
Microorganisms are ubiquitous and can be found in almost every habitat and ecological niche on Earth. They thrive and survive in a broad spectrum of environments and adapt to rapidly changing external conditions. It is of great interest to investigate how microbes adapt to different extreme environments and with modern human space travel, we added a new extreme environment: outer space. Within the last 50 years, technology has provided tools for transporting microbial life beyond Earth’s protective shield in order to study in situ responses to selected conditions of space. This review will focus on halophilic archaea, as, due to their ability to survive in extremes, they are often considered a model group of organisms to study responses to the harsh conditions associated with space. We discuss ground-based simulations, as well as space experiments, utilizing archaea, examining responses and/or resistance to the effects of microgravity and UV in particular. Several halophilic archaea (e.g., Halorubrum chaoviator) have been exposed to simulated and actual space conditions and their survival has been determined as well as the protective effects of halite shown. Finally, the intriguing potential of archaea to survive on other planets or embedded in a meteorite is postulated.
halophilic archaea; space conditions; UV
Analysis of DNA Repair and Protection in the Tardigrade Ramazzottius varieornatus and Hypsibius dujardini after Exposure to UVC Radiation
Horikawa, Daiki D.
Rothschild, Lynn J.
Tardigrades inhabiting terrestrial environments exhibit extraordinary resistance to ionizing radiation and UV radiation although little is known about the mechanisms underlying the resistance. We found that the terrestrial tardigrade Ramazzottius varieornatus is able to tolerate massive doses of UVC irradiation by both being protected from forming UVC-induced thymine dimers in DNA in a desiccated, anhydrobiotic state as well as repairing the dimers that do form in the hydrated animals. In R. varieornatus accumulation of thymine dimers in DNA induced by irradiation with 2.5 kJ/m2 of UVC radiation disappeared 18 h after the exposure when the animals were exposed to fluorescent light but not in the dark. Much higher UV radiation tolerance was observed in desiccated anhydrobiotic R. varieornatus compared to hydrated specimens of this species. On the other hand, the freshwater tardigrade species Hypsibius dujardini that was used as control, showed much weaker tolerance to UVC radiation than R. varieornatus, and it did not contain a putative phrA gene sequence. The anhydrobiotes of R. varieornatus accumulated much less UVC-induced thymine dimers in DNA than hydrated one. It suggests that anhydrobiosis efficiently avoids DNA damage accumulation in R. varieornatus and confers better UV radiation tolerance on this species. Thus we propose that UV radiation tolerance in tardigrades is due to the both high capacities of DNA damage repair and DNA protection, a two-pronged survival strategy.
Evaluation of the LIVE/DEAD BacLight Kit for Detection of Extremophilic Archaea and Visualization of Microorganisms in Environmental Hypersaline Samples
Applied and Environmental Microbiology
Extremophilic archaea were stained with the LIVE/DEAD BacLight kit under conditions of high ionic strength and over a pH range of 2.0 to 9.3. The reliability of the kit was tested with haloarchaea following permeabilization of the cells. Microorganisms in hypersaline environmental samples were detectable with the kit, which suggests its potential application to future extraterrestrial halites.
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