Life2014, 4(3), 511-534; doi:10.3390/life4030511 - published 15 September 2014 Show/Hide Abstract
Abstract: The geomicrobiological characterization of the water column and sediments of Río Tinto (Huelva, Southwestern Spain) have proven the importance of the iron and the sulfur cycles, not only in generating the extreme conditions of the habitat (low pH, high concentration of toxic heavy metals), but also in maintaining the high level of microbial diversity detected in the basin. It has been proven that the extreme acidic conditions of Río Tinto basin are not the product of 5000 years of mining activity in the area, but the consequence of an active underground bioreactor that obtains its energy from the massive sulfidic minerals existing in the Iberian Pyrite Belt. Two drilling projects, MARTE (Mars Astrobiology Research and Technology Experiment) (2003–2006) and IPBSL (Iberian Pyrite Belt Subsurface Life Detection) (2011–2015), were developed and carried out to provide evidence of subsurface microbial activity and the potential resources that support these activities. The reduced substrates and the oxidants that drive the system appear to come from the rock matrix. These resources need only groundwater to launch diverse microbial metabolisms. The similarities between the vast sulfate and iron oxide deposits on Mars and the main sulfide bioleaching products found in the Tinto basin have given Río Tinto the status of a geochemical and mineralogical Mars terrestrial analogue.
Life2014, 4(3), 491-510; doi:10.3390/life4030491 - published 11 September 2014 Show/Hide Abstract
Abstract: Projecting a vision for space radiobiological research necessitates understanding the nature of the space radiation environment and how radiation risks influence mission planning, timelines and operational decisions. Exposure to space radiation increases the risks of astronauts developing cancer, experiencing central nervous system (CNS) decrements, exhibiting degenerative tissue effects or developing acute radiation syndrome. One or more of these deleterious health effects could develop during future multi-year space exploration missions beyond low Earth orbit (LEO). Shielding is an effective countermeasure against solar particle events (SPEs), but is ineffective in protecting crew members from the biological impacts of fast moving, highly-charged galactic cosmic radiation (GCR) nuclei. Astronauts traveling on a protracted voyage to Mars may be exposed to SPE radiation events, overlaid on a more predictable flux of GCR. Therefore, ground-based research studies employing model organisms seeking to accurately mimic the biological effects of the space radiation environment must concatenate exposures to both proton and heavy ion sources. New techniques in genomics, proteomics, metabolomics and other “omics” areas should also be intelligently employed and correlated with phenotypic observations. This approach will more precisely elucidate the effects of space radiation on human physiology and aid in developing personalized radiological countermeasures for astronauts.
Life2014, 4(3), 457-490; doi:10.3390/life4030457 - published 5 September 2014 Show/Hide Abstract
Abstract: The paper offers a design perspective on protocell applications and presents original research that characterizes the life-like qualities of the Bütschli dynamic droplet system, as a particular “species” of protocell. Specific focus is given to the possibility of protocell species becoming a technical platform for designing and engineering life-like solutions to address design challenges. An alternative framing of the protocell, based on process philosophy, sheds light on its capabilities as a technology that can deal with probability and whose ontology is consistent with complexity, nonlinear dynamics and the flow of energy and matter. However, the proposed technical systems do not yet formally exist as products or mature technologies. Their potential applications are therefore experimentally examined within a design context as architectural “projects”—an established way of considering proposals that have not yet been realized, like an extended hypothesis. Exemplary design-led projects are introduced, such as The Hylozoic Ground and Future Venice, which aim to “discover”, rather than “solve”, challenges to examine a set of possibilities that have not yet been resolved. The value of such exploration in design practice is in opening up a set of potential directions for further assessment before complex challenges are procedurally implemented.
Life2014, 4(3), 433-456; doi:10.3390/life4030433 - published 3 September 2014 Show/Hide Abstract
Abstract: The filamentous cyanobacterium, Pseudanabaena, has been shown to produce reticulate patterns that are thought to be the result of its gliding motility. Similar fossilized structures found in the geological record constitute some of the earliest signs of life on Earth. It is difficult to tie these fossils, which are billions of years old, directly to the specific microorganisms that built them. Identifying the physicochemical conditions and microorganism properties that lead microbial mats to form macroscopic structures can lead to a better understanding of the conditions on Earth at the dawn of life. In this article, a cell-based model is used to simulate the formation of reticulate patterns in cultures of Pseudanabaena. A minimal system of long and flexible trichomes capable of gliding motility is shown to be sufficient to produce stable patterns consisting of a network of streams. Varying model parameters indicate that systems with little to no cohesion, high trichome density and persistent movement are conducive to reticulate pattern formation, in conformance with experimental observations.
Abstract: Spring mounds on Earth and on Mars could represent optimal niches of life development. If life ever occurred on Mars, ancient spring deposits would be excellent localities to search for morphological or chemical remnants of an ancient biosphere. In this work, we investigate models of formation and activity of well-exposed spring mounds in the Mechertate-Chrita-Sidi El Hani (MCSH) system, eastern Tunisia. We then use these models to explore possible spring mound formation on Mars. In the MCSH system, the genesis of the spring mounds is a direct consequence of groundwater upwelling, triggered by tectonics and/or hydraulics. As they are oriented preferentially along faults, they can be considered as fault spring mounds, implying a tectonic influence in their formation process. However, the hydraulic pressure generated by the convergence of aquifers towards the surface of the system also allows consideration of an origin as artesian spring mounds. In the case of the MCSH system, our geologic data presented here show that both models are valid, and we propose a combined hydro-tectonic model as the likely formation mechanism of artesian-fault spring mounds. During their evolution from the embryonic (early) to the islet (“island”) stages, spring mounds are also shaped by eolian accumulations and induration processes. Similarly, spring mounds have been suggested to be relatively common in certain provinces on the Martian surface, but their mode of formation is still a matter of debate. We propose that the tectonic, hydraulic, and combined hydro-tectonic models describing the spring mounds at MCSH could be relevant as Martian analogs because: (i) the Martian subsurface may be over pressured, potentially expelling mineral-enriched waters as spring mounds on the surface; (ii) the Martian subsurface may be fractured, causing alignment of the spring mounds in preferential orientations; and (iii) indurated eolian sedimentation and erosional remnants are common features on Mars. The spring mounds further bear diagnostic mineralogic and magnetic properties, in comparison with their immediate surroundings. Consequently, remote sensing techniques can be very useful to identify similar spring mounds on Mars. The mechanisms (tectonic and/or hydraulic) of formation and evolution of spring mounds at the MCSH system are suitable for the proliferation and protection of life respectively. Similarly, life or its resulting biomarkers on Mars may have been protected or preserved under the spring mounds.
Abstract: In polar aprotic organic solvents, fluorine might be an element of choice for life that uses selected fluorinated building blocks as monomers of choice for self-assembling of its catalytic polymers. Organofluorine compounds are extremely rare in the chemistry of life as we know it. Biomolecules, when fluorinated such as peptides or proteins, exhibit a “fluorous effect”, i.e., they are fluorophilic (neither hydrophilic nor lipophilic). Such polymers, capable of creating self-sorting assemblies, resist denaturation by organic solvents by exclusion of fluorocarbon side chains from the organic phase. Fluorous cores consist of a compact interior, which is shielded from the surrounding solvent. Thus, we can anticipate that fluorine-containing “teflon”-like or “non-sticking” building blocks might be monomers of choice for the synthesis of organized polymeric structures in fluorine-rich planetary environments. Although no fluorine-rich planetary environment is known, theoretical considerations might help us to define chemistries that might support life in such environments. For example, one scenario is that all molecular oxygen may be used up by oxidation reactions on a planetary surface and fluorine gas could be released from F-rich magma later in the history of a planetary body to result in a fluorine-rich planetary environment.