David E. Bryant

Direct evidence for the availability of reactive, water soluble phosphorus on the early Earth. H-Phosphinic acid from the Nantan meteorite

Anoxic irradiation of a type IIICD iron meteorite known to contain the phosphide mineral schreibersite (Fe,Ni)3P in the presence of ethanol/water affords the reactive oxyacid H-phosphinic acid (H3PO2) as the dominant phosphorus product.

Electrochemical studies of iron meteorites: phosphorus redox chemistry on the early Earth

The mineral schreibersite, (Fe,Ni)(3)P, a ubiquitous component of iron meteorites. is known to undergo anoxic hydrolytic modification to afford a range Of phosphorus oxyacids. H-phosphonic acid (H3PO3) is the principal hydrolytic product under hydrothermal conditions, as confirmed here by P-31-NMR spectroscopic studies oil shavings of the Seymchan pallasite (Magadan, Russia, 1967), but in the presence of photochemical irradiation I more reduced derivative, H-phosphinic (H3PO2) acid, dominates. The significance Of Such lower oxidation state oxyacids of phosphorus to prebiotic chemistry upon the early Earth lies with the facts that Such forms Of Phosphorus are considerably more Soluble and chemically reactive than orthophosphate, the commonly found form of phosphorus oil Earth, thus allowing nature a mechanism to circumvent the so-called Phosphate Problem. This paper describes the Galvanic corrosion of Fe3P, a hydrolytic modification pathway for schreibersite, leading again to H-phosphinic acid as the key P-containing product. We envisage this pathway to be highly significant within a meteoritic context as iron meteorites are polymetallic composites in which dissimilar metals, with different electrochemical potentials, are connected by all electrically conducting matrix. In the presence of a Suitable electrolyte medium, i.e., salt water, galvanic corrosion call take place. In addition to model electrochemical studies, we also report the first application of the Kelvin technique to map surface potentials of a meteorite sample that allows the electrochemical differentiation of schreibersite inclusions Within an Fe:Ni matrix. Such experiments, coupled with thermodynamic calculations, may allow LIS to better understand the chemical redox behaviour of meteoritic components with early Earth environments.

Phosphate Activation via Reduced Oxidation State Phosphorus (P). Mild Routes to Condensed-P Energy Currency Molecules.

The emergence of mechanisms for phosphorylating organic and inorganic molecules is a key step en route to the earliest living systems. At the heart of all contemporary biochemical systems reside reactive phosphorus (P) molecules (such as adenosine triphosphate, ATP) as energy currency molecules to drive endergonic metabolic processes and it has been proposed that a predecessor of such molecules could have been pyrophosphate [P2O74−; PPi(V)]. Arguably the most geologically plausible route to PPi(V) is dehydration of orthophosphate, Pi(V), normally a highly endergonic process in the absence of mechanisms for activating Pi(V). One possible solution to this problem recognizes the presence of reactive-P containing mineral phases, such as schreibersite [(Fe,Ni)3P] within meteorites whose abundance on the early Earth would likely have been significant during a putative Hadean-Archean heavy bombardment. Here, we propose that the reduced oxidation state P-oxyacid, H-phosphite [HPO32−; Pi(III)] could have activated Pi(V) towards condensation via the intermediacy of the condensed oxyacid pyrophosphite [H2P2O52−; PPi(III)]. We provide geologically plausible provenance for PPi(III) along with evidence of its ability to activate Pi(V) towards PPi(V) formation under mild conditions (80 °C) in water.

On the origin of the Murchison meteorite phosphonates. Implications for pre-biotic chemistry

Ab initio calculations, combined with experimental studies on the anaerobic hydrolysis of phosphaalkynes under thermal and photochemical conditions suggest a potential, exogenous source of reduced oxidation state phosphorus for the early Earth.

Selective Phosphonylation of 5′-Adenosine Monophosphate (5′-AMP) via Pyrophosphite [PPi(III)]

We describe here experiments which demonstrate the selective phospho-transfer from a plausibly prebiotic condensed phosphorus (P) salt, pyrophosphite [H2P2O52−; PPi(III)], to the phosphate group of 5′-adenosine mono phosphate (5′-AMP). We show further that this P-transfer process is accelerated both by divalent metal ions (M2+) and by organic co-factors such as acetate (AcO−). In this specific case of P-transfer from PPi(III) to 5′-AMP, we show a synergistic enhancement of transfer in the combined presence of M2+ & AcO−. Isotopic labelling studies demonstrate that hydrolysis of the phosphonylated 5′-AMP, [P(III)P(V)-5′-AMP], proceeds via nuceophilic attack of water at the Pi(III) terminus.

Special Issue: Abstracts from the 9th European Workshop on Astrobiology, Brussels, October 12–14, 2009

Lichens have been proposed as one of the groups of organisms able to cope with outer space conditions. This is based on the fact that they are extremophiles. Vagrant lichens or erratic lichens live unattached to the substrate and are well known from the continental deserts and arid areas of Middle Asia, Eurasia, North America and Northern Africa. For this work we have selected Aspicilia fruticulosa, a vagrant lichen that typically develops a globular fruticose and compact thallus up to 2.5 cm diameter. We have selected this lichen species to test the survival capacity to harsh space conditions in the Lithopanspermia experiment, which was integrated on board of Biopan (Foton M3 satellite, September 2007), a facility developed by ESA to expose exo-astrobiology experiments to space environment in a low Earth orbit (LEO).Tardigrades (water bears) are polyextremophilic, cosmopolitan eukaroytic metazoans that are able to survive different types of extreme conditions, ranging from extreme temperature ranges from -273 to >100°C, 1,000 times more ionizing radiation than most other animals such as humans, and complete desiccation for long periods. Tardigrades are one of the few groups of organisms on our planet that are capable of reversibly suspending their metabolism and entering into a state of cryptobiosis, where metabolism has been lowered to immeasurable levels at water content below 1% of the normal hydration. Due to these traits, they belong to one of the few species on planet Earth that can survive some of the extreme conditions found in outer space, and may thus serve as important model organisms to explore the survival rate of species from planet Earth on other planetary bodies. Although the biology and the survival strategies of tardigrades have been studied in greater detail, our knowledge about the endogenous microbiology of tardigrades and its potential role for its survival is rather scarce. However, we anticipate that a combined research on the biology in general and the microbiology of tardigrades could possibly add interesting insights into the survival strategies of tardigrades. For example, to obtain novel insights into the role of prokaryotes as a food source for tardigrades in general, as fundamental parts of the intestinal gut flora that may help degrade ingested substrates, secrete valuable biochemical compounds like vitamins, or as pathogens that may decrease their survival possibilities. Another intriguing question is if prokaryotes in tardigrades shipped to outer space would also survive, and if synergistic interactions may take place that could influence the survival possibilities of both tardigrades and the prokaryotes in an alien system. For example, would it be possible to feed/infect tardigrades with chemolithoautotrophic species that are able to metabolize different types of inorganic compunds and would these be able to grow again on inorganic particles after the cryptobiotic state and thus serve as a continuous food source for the tardigrades in an alien environment? In order to trace such fascinating, though rather speculative issues, several basic studies and method developments must be performed so that reliable tools for microbial involvement under different stress reactions can be used in these kinds of astrobiological experiments. We have started to compare different analytical tools to explore the microbiological composition and dynamics in tardigrades, ranging from nucleic acid based tools and PCR for sequencing and quantification of 16S rRNA genes, microcalorimetric energy measurements as a nondisruptive indicator for responses to different conditions, to microscopic studies for in situ visualization of prokaryotes on the tardigrades. We are currently in the process of evaluating these methods on tardigrades exposed to different stress conditions and fed with different microorganisms in order to explore if tardigrades are dependent on a specific microflora for optimal survival. In future, we plan to design elaborate experiments to explore further the effect of the microflora on the survival rates of tardigrades under different simulated extreme conditions on Earth, as well as in outer space.The 9th European Workshop on Astrobiology “EANA’09”, annual meeting of European Astrobiology Network Association EANA ( ), was held in the Royal Library of Brussels, Belgium, from October 12–14, 2009, hosted by the Belgian Astrobiology Group BAG ( ). A main section of EANA’09 was devoted to sessions paying homage to Darwin’s theory of evolution, thereby celebrating the 150th anniversary of the first publication of the path-finding book “The Origin of Species by Means of Natural Selection” and the anniversary of the 200th birthday of Charles Darwin: 1. In Homage to Darwin’s Theory of Evolution: Prebiotic Chemical Evolution 2. In Homage to Darwin’s Theory of Evolution: Early Biosphere and Biological EvolutionThe ability of certain microbial species to survive adverse conditions such as radiation and desiccation has been an important research subject for astrobiology. The reason for this is perhaps the traditional view that life at the surface of planets, which generally have thin atmospheres, low amounts of water and intense radiation, might be possible. Interestingly, many highly resistant organisms such as Deinococcus geothermalis or D. radiodurans have not been isolated from environments resembling in any respect conditions which are known to exist on Mars or other terrestrial planets. Many of these organisms are heterotrophs relying on the availability of complex organic molecules which are scarce -if existent at all- on planets such as Mars. Although these organisms are important to understand the tenacity of certain forms of life, their role in potential Martian ecosystems might not be entirely realistic. If present, life on Mars could be located at either the shallow or deep subsurface were conditions are “less extreme” as compared to the surface of the planet. The subsurface’s porous matrix would offer increased physical protection to environmental stresses as well as higher water availability. Potential life forms thriving in these environments, would obtain their energy from redox disequilibria caused by chemical species at different oxidation states. In the case of Mars, the presence of iron in both oxidized and reduced forms as well as the presence of several forms of sulfur might allow life forms which could utilize these compounds in a hypothetical energy conserving process. Furthermore, the presence of sulfates suggests that water has been abundant at intermittent stages during Mars history although it is known to be scarce at present. Based on these assumptions, we are studying several species of iron-sulfur bacteria including Acidithiobacillus sp. and Sulfobacillus sp. These bacteria are chemolithoautotrophs, able to utilize iron and sulfur compounds in various forms for their energy requirements and therefore might be more relevant for Mars. The resistant model organism Deinococcus geothermalis is used for comparative purposes. Microbial colonization as a biofilm is simulated in porous materials consisting of Mars-relevant minerals. Key physiological responses to hydration/dehydration cycles and later simulated Martian environmental conditions are studied using both microbiological and physicochemical techniques. These techniques include: fluorescence microscopy, confocal laser scanning microscopy, colorimetric assays, ion chromatography and microcalorimetry. Results with iron- sulfur biofilms grown in absence of a porous environment suggests low resistance to de-hydration, however, the role of minerals and high specific surfaces of porous environments on microbial activity during or after hydration stress remains an open question which is currently under investigation.