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Life, Volume 3, Issue 4 (December 2013), Pages 518-549

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Editorial

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Open AccessEditorial Horizontal Gene Transfer and Its Part in the Reorganisation of Genetics during the LUCA Epoch
Life 2013, 3(4), 518-523; doi:10.3390/life3040518
Received: 20 October 2013 / Accepted: 22 October 2013 / Published: 28 October 2013
Cited by 2 | PDF Full-text (37 KB) | HTML Full-text | XML Full-text
Abstract
Currently there are five known mechanisms of horizontal gene transfer (HGT): transduction, conjugation, transformation, gene transfer agents and membrane vesicle transfer. The question here is: what part did HGT play in the reorganisation of genetics during the last universal common ancestor (LUCA) [...] Read more.
Currently there are five known mechanisms of horizontal gene transfer (HGT): transduction, conjugation, transformation, gene transfer agents and membrane vesicle transfer. The question here is: what part did HGT play in the reorganisation of genetics during the last universal common ancestor (LUCA) epoch? LUCA is a construct to explain the origin of the three domains of life; namely Archaea, Bacteria and Eukarya. This editorial offers a general introduction to the relevance and ultimate significance of HGT in relation to the LUCA. [...] Full article
(This article belongs to the Special Issue Horizontal Gene Transfer and the Last Universal Common Ancestor)

Research

Jump to: Editorial

Open AccessArticle Distance and Size Perception in Astronauts during Long-Duration Spaceflight
Life 2013, 3(4), 524-537; doi:10.3390/life3040524
Received: 7 November 2013 / Revised: 3 December 2013 / Accepted: 9 December 2013 / Published: 13 December 2013
Cited by 5 | PDF Full-text (226 KB) | HTML Full-text | XML Full-text
Abstract
Exposure to microgravity during spaceflight is known to elicit orientation illusions, errors in sensory localization, postural imbalance, changes in vestibulo-spinal and vestibulo-ocular reflexes, and space motion sickness. The objective of this experiment was to investigate whether an alteration in cognitive visual-spatial processing, [...] Read more.
Exposure to microgravity during spaceflight is known to elicit orientation illusions, errors in sensory localization, postural imbalance, changes in vestibulo-spinal and vestibulo-ocular reflexes, and space motion sickness. The objective of this experiment was to investigate whether an alteration in cognitive visual-spatial processing, such as the perception of distance and size of objects, is also taking place during prolonged exposure to microgravity. Our results show that astronauts on board the International Space Station exhibit biases in the perception of their environment. Objects’ heights and depths were perceived as taller and shallower, respectively, and distances were generally underestimated in orbit compared to Earth. These changes may occur because the perspective cues for depth are less salient in microgravity or the eye-height scaling of size is different when an observer is not standing on the ground. This finding has operational implications for human space exploration missions. Full article
(This article belongs to the Special Issue Response of Terrestrial Life to Space Conditions)
Open AccessArticle Simulations of Prebiotic Chemistry under Post-Impact Conditions on Titan
Life 2013, 3(4), 538-549; doi:10.3390/life3040538
Received: 4 November 2013 / Revised: 6 December 2013 / Accepted: 9 December 2013 / Published: 17 December 2013
Cited by 2 | PDF Full-text (364 KB) | HTML Full-text | XML Full-text
Abstract
The problem of how life began can be considered as a matter of basic chemistry. How did the molecules of life arise from non-biological chemistry? Stanley Miller’s famous experiment in 1953, in which he produced amino acids under simulated early Earth conditions, [...] Read more.
The problem of how life began can be considered as a matter of basic chemistry. How did the molecules of life arise from non-biological chemistry? Stanley Miller’s famous experiment in 1953, in which he produced amino acids under simulated early Earth conditions, was a huge leap forward in our understanding of this problem. Our research first simulated early Earth conditions based on Miller’s experiment and we then repeated the experiment using Titan post-impact conditions. We simulated conditions that could have existed on Titan after an asteroid strike. Specifically, we simulated conditions after a potential strike in the subpolar regions of Titan that exhibit vast methane-ethane lakes. If the asteroid or comet was of sufficient size, it would also puncture the icy crust and bring up some of the subsurface liquid ammonia-water mixture. Since, O’Brian, Lorenz and Lunine showed that a liquid water-ammonia body could exist between about 102–104 years on Titan after an asteroid impact we modified our experimental conditions to include an ammonia-water mixture in the reaction medium. Here we report on the resulting amino acids found using the Titan post-impact conditions in a classical Miller experimental reaction set-up and how they differ from the simulated early Earth conditions. Full article

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