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Life, Volume 4, Issue 1 (March 2014), Pages 1-116

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Editorial

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Open AccessEditorial Letter from the New Editor-in-Chief
Life 2014, 4(1), 1-3; doi:10.3390/life4010001
Received: 2 January 2014 / Accepted: 6 January 2014 / Published: 8 January 2014
Cited by 3 | PDF Full-text (23 KB) | HTML Full-text | XML Full-text
Abstract
It is my great pleasure to serve as the new Editor-in-Chief of Life, a journal concerned with fundamental questions on the origins and nature of life, evolution of biosystems and astrobiology. With my experience as Executive Editor, Senior Editor and Guest Editor of
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It is my great pleasure to serve as the new Editor-in-Chief of Life, a journal concerned with fundamental questions on the origins and nature of life, evolution of biosystems and astrobiology. With my experience as Executive Editor, Senior Editor and Guest Editor of so many successful special issues (some of them in MDPI journals [1–6]), I am committed to making the journal a success, with the launch of exciting special issues, publication of high quality papers, as well as inclusion of the journal in major indexing and abstracting services. In this editorial, I present my view and plans for the journal. [...] Full article
Open AccessEditorial Acknowledgement to Reviewers of Life in 2013
Life 2014, 4(1), 105-106; doi:10.3390/life4010105
Received: 27 February 2014 / Accepted: 27 February 2014 / Published: 27 February 2014
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Abstract The editors of Life would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2013. [...] Full article

Research

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Open AccessArticle The Formation of Jupiter, the Jovian Early Bombardment and the Delivery of Water to the Asteroid Belt: The Case of (4) Vesta
Life 2014, 4(1), 4-34; doi:10.3390/life4010004
Received: 1 November 2013 / Revised: 26 December 2013 / Accepted: 16 January 2014 / Published: 28 January 2014
Cited by 8 | PDF Full-text (11412 KB) | HTML Full-text | XML Full-text
Abstract
The asteroid (4) Vesta, parent body of the Howardite-Eucrite-Diogenite meteorites, is one of the first bodies that formed, mostly from volatile-depleted material, in the Solar System. The Dawn mission recently provided evidence that hydrated material was delivered to Vesta, possibly in a continuous
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The asteroid (4) Vesta, parent body of the Howardite-Eucrite-Diogenite meteorites, is one of the first bodies that formed, mostly from volatile-depleted material, in the Solar System. The Dawn mission recently provided evidence that hydrated material was delivered to Vesta, possibly in a continuous way, over the last 4 Ga, while the study of the eucritic meteorites revealed a few samples that crystallized in presence of water and volatile elements. The formation of Jupiter and probably its migration occurred in the period when eucrites crystallized, and triggered a phase of bombardment that caused icy planetesimals to cross the asteroid belt. In this work, we study the flux of icy planetesimals on Vesta during the Jovian Early Bombardment and, using hydrodynamic simulations, the outcome of their collisions with the asteroid. We explore how the migration of the giant planet would affect the delivery of water and volatile materials to the asteroid and we discuss our results in the context of the geophysical and collisional evolution of Vesta. In particular, we argue that the observational data are best reproduced if the bulk of the impactors was represented by 1–2 km wide planetesimals and if Jupiter underwent a limited (a fraction of au) displacement. Full article
(This article belongs to the Special Issue Planet Formation and the Rise of Life)
Figures

Open AccessArticle Neuronal Activity in the Subthalamic Cerebrovasodilator Area under Partial-Gravity Conditions in Rats
Life 2014, 4(1), 107-116; doi:10.3390/life4010107
Received: 14 January 2014 / Revised: 18 February 2014 / Accepted: 26 February 2014 / Published: 4 March 2014
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Abstract
The reduced-gravity environment in space is known to cause an upward shift in body fluids and thus require cardiovascular adaptations in astronauts. In this study, we recorded in rats the neuronal activity in the subthalamic cerebrovasodilator area (SVA), a key area that controls
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The reduced-gravity environment in space is known to cause an upward shift in body fluids and thus require cardiovascular adaptations in astronauts. In this study, we recorded in rats the neuronal activity in the subthalamic cerebrovasodilator area (SVA), a key area that controls cerebral blood flow (CBF), in response to partial gravity. “Partial gravity” is the term that defines the reduced-gravity levels between 1 g (the unit gravity acceleration on Earth) and 0 g (complete weightlessness in space). Neuronal activity was recorded telemetrically through chronically implanted microelectrodes in freely moving rats. Graded levels of partial gravity from 0.4 g to 0.01 g were generated by customized parabolic-flight maneuvers. Electrophysiological signals in each partial-gravity phase were compared to those of the preceding 1 g level-flight. As a result, SVA neuronal activity was significantly inhibited by the partial-gravity levels of 0.15 g and lower, but not by 0.2 g and higher. Gravity levels between 0.2–0.15 g could represent a critical threshold for the inhibition of neurons in the rat SVA. The lunar gravity (0.16 g) might thus trigger neurogenic mechanisms of CBF control. This is the first study to examine brain electrophysiology with partial gravity as an experimental parameter. Full article
(This article belongs to the Special Issue Response of Terrestrial Life to Space Conditions)

Review

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Open AccessReview Setting the Stage for Habitable Planets
Life 2014, 4(1), 35-65; doi:10.3390/life4010035
Received: 25 October 2013 / Revised: 10 February 2014 / Accepted: 17 February 2014 / Published: 21 February 2014
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Abstract
Our understanding of the processes that are relevant to the formation and maintenance of habitable planetary systems is advancing at a rapid pace, both from observation and theory. The present review focuses on recent research that bears on this topic and includes discussions
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Our understanding of the processes that are relevant to the formation and maintenance of habitable planetary systems is advancing at a rapid pace, both from observation and theory. The present review focuses on recent research that bears on this topic and includes discussions of processes occurring in astrophysical, geophysical and climatic contexts, as well as the temporal evolution of planetary habitability. Special attention is given to recent observations of exoplanets and their host stars and the theories proposed to explain the observed trends. Recent theories about the early evolution of the Solar System and how they relate to its habitability are also summarized. Unresolved issues requiring additional research are pointed out, and a framework is provided for estimating the number of habitable planets in the Universe. Full article
(This article belongs to the Special Issue Planet Formation and the Rise of Life)
Open AccessReview On the Response of Halophilic Archaea to Space Conditions
Life 2014, 4(1), 66-76; doi:10.3390/life4010066
Received: 24 January 2014 / Revised: 10 February 2014 / Accepted: 17 February 2014 / Published: 21 February 2014
Cited by 2 | PDF Full-text (112 KB) | HTML Full-text | XML Full-text
Abstract
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
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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. Full article
(This article belongs to the Special Issue Response of Terrestrial Life to Space Conditions)
Open AccessReview Anaerobic Thermophiles
Life 2014, 4(1), 77-104; doi:10.3390/life4010077
Received: 3 June 2013 / Revised: 10 January 2014 / Accepted: 26 January 2014 / Published: 26 February 2014
Cited by 6 | PDF Full-text (1850 KB) | HTML Full-text | XML Full-text
Abstract
The term “extremophile” was introduced to describe any organism capable of living and growing under extreme conditions. With the further development of studies on microbial ecology and taxonomy, a variety of “extreme” environments have been found and an increasing number of extremophiles are
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The term “extremophile” was introduced to describe any organism capable of living and growing under extreme conditions. With the further development of studies on microbial ecology and taxonomy, a variety of “extreme” environments have been found and an increasing number of extremophiles are being described. Extremophiles have also been investigated as far as regarding the search for life on other planets and even evaluating the hypothesis that life on Earth originally came from space. The first extreme environments to be largely investigated were those characterized by elevated temperatures. The naturally “hot environments” on Earth range from solar heated surface soils and water with temperatures up to 65 °C, subterranean sites such as oil reserves and terrestrial geothermal with temperatures ranging from slightly above ambient to above 100 °C, to submarine hydrothermal systems with temperatures exceeding 300 °C. There are also human-made environments with elevated temperatures such as compost piles, slag heaps, industrial processes and water heaters. Thermophilic anaerobic microorganisms have been known for a long time, but scientists have often resisted the belief that some organisms do not only survive at high temperatures, but actually thrive under those hot conditions. They are perhaps one of the most interesting varieties of extremophilic organisms. These microorganisms can thrive at temperatures over 50 °C and, based on their optimal temperature, anaerobic thermophiles can be subdivided into three main groups: thermophiles with an optimal temperature between 50 °C and 64 °C and a maximum at 70 °C, extreme thermophiles with an optimal temperature between 65 °C and 80 °C, and finally hyperthermophiles with an optimal temperature above 80 °C and a maximum above 90 °C. The finding of novel extremely thermophilic and hyperthermophilic anaerobic bacteria in recent years, and the fact that a large fraction of them belong to the Archaea has definitely made this area of investigation more exciting. Particularly fascinating are their structural and physiological features allowing them to withstand extremely selective environmental conditions. These properties are often due to specific biomolecules (DNA, lipids, enzymes, osmolites, etc.) that have been studied for years as novel sources for biotechnological applications. In some cases (DNA-polymerase, thermostable enzymes), the search and applications successful exceeded preliminary expectations, but certainly further exploitations are still needed. Full article
(This article belongs to the Special Issue Extremophiles and Extreme Environments)

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