| 1. |
- Jönsson, K. Ingemar, 1959-
(författare)
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Tardigrades as a potential model organism in space research
- 2007
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Ingår i: Astrobiology. - 1531-1074 .- 1557-8070. - 1531-1074 ; 7:5, s. 757-766
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Tidskriftsartikel (refereegranskat)abstract
- Exposure of living organisms to open space requires a high level of tolerance to desiccation, cold, and radiation. Among animals, only anhydrobiotic species can fulfill these requirements. The invertebrate phylum Tardigrada includes many anhydrobiotic species, which are adapted to survive in very dry or cold environmental conditions. As a likely by-product of the adaptations for desiccation and freezing, tardigrades also show a very high tolerance to a number of other, unnatural conditions, including exposure to ionizing radiation. This makes tardigrades an interesting candidate for experimental exposure to open space. This paper reviews the tolerances that make tardigrades suitable for astrobiological studies and the reported radiation tolerance in other anhydrobiotic animals. Several studies have shown that tardigrades can survive gamma-irradiation well above 1 kilogray, and desiccated and hydrated (active) tardigrades respond similarly to irradiation. Thus, tolerance is not restricted to the dry anhydrobiotic state, and I discuss the possible involvement of an efficient, but yet undocumented, mechanism for DNA repair. Other anhydrobiotic animals (Artemia, Polypedium), when dessicated, show a higher tolerance to gamma-irradiation than hydrated animals, possibly due to the presence of high levels of the protective disaccharide trehalose in the dry state. Tardigrades and other anhydrobiotic animals provide a unique opportunity to study the effects of space exposure on metabolically inactive but vital metazoans.
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| 2. |
- Jönsson, K. Ingemar
(författare)
-
Tardigrades as a potential model organism in space research
- 2007
-
Ingår i: Astrobiology. - : Mary Ann Liebert Inc.. - 1531-1074 .- 1557-8070. ; 7:5, s. 757-766
-
Tidskriftsartikel (refereegranskat)abstract
- Exposure of living organisms to open space requires a high level of tolerance to desiccation, cold, and radiation. Among animals, only anhydrobiotic species can fulfill these requirements. The invertebrate phylum Tardigrada includes many anhydrobiotic species, which are adapted to survive in very dry or cold environmental conditions. As a likely by-product of the adaptations for desiccation and freezing, tardigrades also show a very high tolerance to a number of other, unnatural conditions, including exposure to ionizing radiation. This makes tardigrades an interesting candidate for experimental exposure to open space. This paper reviews the tolerances that make tardigrades suitable for astrobiological studies and the reported radiation tolerance in other anhydrobiotic animals. Several studies have shown that tardigrades can survive gamma-irradiation well above 1 kilogray, and desiccated and hydrated (active) tardigrades respond similarly to irradiation. Thus, tolerance is not restricted to the dry anhydrobiotic state, and I discuss the possible involvement of an efficient, but yet undocumented, mechanism for DNA repair. Other anhydrobiotic animals (Artemia, Polypedium), when dessicated, show a higher tolerance to gamma-irradiation than hydrated animals, possibly due to the presence of high levels of the protective disaccharide trehalose in the dry state. Tardigrades and other anhydrobiotic animals provide a unique opportunity to study the effects of space exposure on metabolically inactive but vital metazoans.
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| 3. |
- Poole, Anthony M., et al.
(författare)
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Can identification of a fourth domain of life be made from sequence data alone, and could it be done on mars?
- 2007
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Ingår i: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; 7:5, s. 801-814
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Forskningsöversikt (refereegranskat)abstract
- A central question in astrobiology is whether life exists elsewhere in the universe. If so, is it related to Earth life? Technologies exist that enable identification of DNA- or RNA-based microbial life directly from environmental samples here on Earth. Such technologies could, in principle, be applied to the search for life elsewhere; indeed, efforts are underway to initiate such a search. However, surveying for nucleic acid-based life on other planets, if attempted, must be carried out with caution, owing to the risk of contamination by Earth-based life. Here we argue that the null hypothesis must be that any DNA discovered and sequenced from samples taken elsewhere in the universe are Earth-based contaminants. Experience from studies of low-biomass ancient DNA demonstrates that some results, by their very nature, will not enable complete rejection of the null hypothesis. In terms of eliminating contamination as an explanation of the data, there may be value in identification of sequences that lie outside the known diversity of the three domains of life. We therefore have examined whether a fourth domain could be readily identified from environmental DNA sequence data alone. We concluded that, even on Earth, this would be far from trivial, and we illustrate this point by way of examples drawn from the literature. Overall, our conclusions do not bode well for planned PCR-based surveys for life on Mars, and we argue that other independent biosignatures will be essential in corroborating any claims for the presence of life based on nucleic acid sequences.
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| 4. |
- Siljeström, Sandra, et al.
(författare)
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ToF-SIMS Possibilities in Geobiology
- 2008
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Ingår i: Astrobiology. - : Mary Ann Liebert Inc. - 1531-1074 .- 1557-8070. ; , s. 329-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Signs of earliest life on Earth are often controversial. Organic biomarkers, which are widely used to identify biological traces in geological samples, can provide additional information. We present examples of how Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) can be used on its own and in combination with other techniques to detect biomarkers in a variety of samples, including crude oils and microbial cells. ToF-SIMS with its unique combination of absolute sensitivity, high mass resolution and imaging capabilities can help answer geobiological questions and may ultimately be applied to Early Earth and extraterrestrial samples.
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