While some portions of the garnet lair may have formed abiotically, the complex network of tunnels—which includes passages linking them—suggest it was at least partly developed by endoliths, a group of microorganisms known to live within hard materials like rock, shell, and bone.
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However, due to the high free energy change of thioester's hydrolysis and correspondingly their low equilibrium constants, it is unlikely that these compounds could have accumulated abiotically to any significant extent especially in hydrothermal vent conditions.
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Mercury methylation is the process of forming methylmercury (MeHg). The methylation of mercury can occur abiotically or biotically. Biotically, the primary methylators of mercury are sulfate-reducing and iron-reducing bacteria. Three mechanisms have been proposed for the biotic methylation of mercury by sulfate-reducing bacteria.
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There are several chemical processes that happen abiotically (chemical reactions), as well as biotically (microbial or enzyme mediated reactions). For example, oxidation-reduction (redox) reactions can occur simply through the reactions of elements, or by oxidizing/reducing bacteria. The transformations and turnover of elements between sediments and water occur through abiotic chemical processes and microbiological chemical processes.
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The abiotic processes include the rusting of iron-bearing metals, where Fe2+ is abiotically oxidized to Fe3+ in the presence of oxygen, and the reduction of Fe3+ to Fe2+ by iron-sulfide minerals. The biological cycling of Fe2+ is done by iron oxidizing and reducing microbes.Kappler, Andreas; Straub, Kristina L. (2005-01-01). "Geomicrobiological Cycling of Iron".
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Proteinoids, or thermal proteins, are protein-like, often cross-linked molecules formed abiotically from amino acids. Sidney W. Fox initially proposed that they may have been precursors to the first living cells (protocells). The term was also used in the 1960s to describe peptides that are shorter than twenty amino acids found in hydrolysed protein, but this term is no longer commonly used.
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As the spots expand, mycelial growth expands into parenchyma cells, further killing cells within the head. Later stages of disease have external masses of mycelium among clumps of black sporangia, dispersing spores abiotically, and by birds. The diseased heads can completely rot in 3 to 7 days. Rhizopus microsporus has been found to be the species involved in Rhizopus Ear Rot of maize as well.
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Non-'peakists' can be divided into several different categories based on their specific criticism of peak oil. Some claim that any peak will not come soon or have a dramatic effect on the world economies. Others claim we will not reach a peak for technological reasons, while still others claim our oil reserves are quickly regenerated abiotically. Monthly world oil supply data from 1995 to 2008.
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In dihaloelimination the electron donor (H2 in this case) is used to remove two halogens from adjacent carbons that are double bonded. 1,2,3-trichloropropane is reduced to allyl chloride by D. lykanthroporepellens, and further transformed abiotically to allyl alcohol in the presence of water (other abiotic reactions can occur). The carbon source has not been determined for this species but other organisms within Chloroflexi use CO2 as a carbon source.
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Ferrous iron is a soluble form of iron that is stable at extremely low pHs or under anaerobic conditions. Under aerobic, moderate pH conditions ferrous iron is oxidized spontaneously to the ferric () form and is hydrolyzed abiotically to insoluble ferric hydroxide (). There are three distinct types of ferrous iron-oxidizing microbes. The first are acidophiles, such as the bacteria Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans, as well as the archaeon Ferroplasma.
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There are two main types of inorganic carbon that are found in the oceans. Dissolved inorganic carbon (DIC) is made up of bicarbonate (HCO3−), carbonate (CO32−) and carbon dioxide (including both dissolved CO2 and carbonic acid H2CO3). DIC can be converted to particulate inorganic carbon (PIC) through precipitation of CaCO3 (biologically or abiotically). DIC can also be converted to particulate organic carbon (POC) through photosynthesis and chemoautotrophy (i.e.
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The spontaneous formation of complex polymers from abiotically generated monomers under the conditions posited by the "soup" theory is not at all a straightforward process. Besides the necessary basic organic monomers, compounds that would have prohibited the formation of polymers were formed in high concentration during the Miller–Urey and Oró experiments. The Miller experiment, for example, produces many substances that would undergo cross- reactions with the amino acids or terminate the peptide chain.
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PLA is degraded abiotically by three mechanisms: # Hydrolysis: The ester groups of the main chain are cleaved, thus reducing molecular weight. # Thermal degradation: A complex phenomenon leading to the appearance of different compounds such as lighter molecules and linear and cyclic oligomers with different Mw, and lactide. # Photodegradation: UV radiation induces degradation. This is a factor mainly where PLA is exposed to sunlight in its applications in plasticulture, packaging containers and films.
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The trifluoromethyl group occurs in certain pharmaceuticals, drugs, and abiotically synthesized natural fluorocarbon based compounds. The medicinal use of the trifloromethyl group dates from 1928, although research became more intense in the mid-1940s. The trifluoromethyl group is often used as a bioisostere to create derivatives by replacing a chloride or a methyl group. This can be used to adjust the steric and electronic properties of a lead compound, or to protect a reactive methyl group from metabolic oxidation.
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More currently, the microbial loop is considered to be more extended. Chemical compounds in typical bacteria (such as DNA, lipids, sugars, etc.) and similar values of C:N ratios per particle are found in the microparticles formed abiotically. Microparticles are a potentially attractive food source to bacterivorous plankton. If this is the case, the microbial loop can be extended by the pathway of direct transfer of dissolved organic matter (DOM) via abiotic microparticle formation to higher trophic levels.
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The spontaneous formation of complex polymers from abiotically generated monomers under the conditions posited by the "soup" theory is not at all a straightforward process. Besides the necessary basic organic monomers, compounds that would have prohibited the formation of polymers were also formed in high concentration during the Miller–Urey and Joan Oró experiments. The Miller–Urey experiment, for example, produces many substances that would react with the amino acids or terminate their coupling into peptide chains.
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Collectively these multiple observations lead the authors to conclude that they were produced by "biological activity" more than 3.77 billion years ago. This conclusion was greeted with approval, and with skepticism. The authors vigorously defended their conclusions, and are confident that their conclusions will stand the test of time. It was reported in a 2019 paper that hematite tubes and filaments with the same shape and chemical makeup can be produced abiotically by chemical gardens, which may form naturally in some hydrothermal settings.
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The transition of iron between Fe(II) and Fe(III) in aquatic systems interacts with the freshwater phosphorus cycle. With oxygen in the water, Fe(II) gets oxidized to Fe(III), either abiotically or by microbes via lithotrophic oxidation. Fe(III) can form iron hydroxides, which bind tightly to phosphorus, removing it from the bioavailable phosphorus pool, limiting primary productivity. In anoxic conditions, Fe(III) can reduced, used by microbes to be the final electron acceptor from either organic carbon or H2.
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Her group began to study organic films at aerosol water-air interfaces, using surface reflection infrared spectroscopy to examine differences in phenylalanine ionisation in the bulk and at the water surface. Vaida's Ph.D. student, Elizabeth Griffith, found that peptide bonds at the surface of water would be generated nonenzymatically. In 2007 she was appointed distinguished lecturer at Sigma Xi Distinguished Lecturer University of Colorado Boulder. She studied how sunlight can abiotically provide the prebiotic reactions essential for the evolution of life.
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For example, carbon in the interstellar medium and solar nebula partition into distinct states based on thermodynamic favorability. Measuring site-specific isotope enrichments of carbon from organic molecules extracted from carbonaceous chondrites can elucidate where each carbon atom comes from, and how organic molecules can be synthesized abiotically. More broadly, these isotope enrichments can provide information about physical processes in the region where the molecular precursors were formed, and where the molecule formed in the solar system (i.e., nucleosynthetic heterogeneity, mass independent fractionation, self-shielding, etc.).
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Bacteria are more likely to contain such enzymes because of their strong selection for new enzymes and metabolic pathways that supply essential nutrients. In addition, genes move horizontally within microbial populations, spreading newly evolved degradation pathways. Some transformations, particularly substitutions, can proceed both biotically and abiotically, although enzyme-catalyzed reactions typically reach higher rates. For example, the hydrolytic dechlorination of atrazine to hydroxyatrazine in soil by atrazine-dechlorinating bacterial enzymes reached a second-order rate constant of 105/mole/second, likely dominating in the environment.
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In Archaean oceans, phosphoenolpyruvate may have been present abiotically. A simple diagram demonstrating the final step of glycolysis, the transfer of a phosphate group from phosphoenolpyruvate (PEP) to adenosine diphosphate (ADP) by pyruvate kinase, yielding one molecule of pyruvate and one molecule of ATP.In yeast cells, the interaction of yeast pyruvate kinase (YPK) with PEP and its allosteric effector Fructose 1,6-bisphosphate (FBP,) was found to be enhanced by the presence of Mg2+. Therefore, Mg2+ was concluded to be an important cofactor in the catalysis of PEP into pyruvate by pyruvate kinase.
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The Lost City Hydrothermal Field, often referred to simply as Lost City, is an area of marine alkaline hydrothermal vents located on the Atlantis Massif at the intersection between the Mid-Atlantic Ridge and the Atlantis Transform Fault, in the Atlantic Ocean. It is a long-lived site of active and inactive ultramafic-hosted serpentinization, abiotically producing many simple molecules such as methane and hydrogen which are fundamental to microbial life. As such it has generated scientific interest as a prime location for investigating the origin of life on Earth and other planets similar to it.
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Samples taken from different parts of an organism or an organ can simultaneously be analysed and compared, on the same blot, giving a clear picture of the distribution of enzyme activity. With the same simplicity, corresponding tissues taken from normally and biotically- or abiotically- stressed individuals can be compared for enzyme stimulation or induction. Furthermore, zymoblots can be very helpful in cytochemodissection studies aiming at localising enzymes within cells. Cell fractions representing different parts of the cell (nuclei, mitochondria, lysosomes, peroxisomes, Golgi bodies, cytosol,... etc.) can be tested for a host of enzymes in a relatively short time.
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D. lykanthroporepellens is strictly anaerobic and uses hydrogen as an electron donor. It has been cultured in an anaerobic basal medium at 30 °C in the dark. It is able to reductively dehalogenate aliphatic alkanes (non- aromatic alkanes) such as 1,2,3-trichloropropane (reduces it to allyl chloride which abiotically transforms in the presence of water to allyl alcohol). Two strains (BL-DC-9T and BL-DC-8) were isolated from a Superfund site in Baton Rouge, Louisiana in 2009 by Moe, Yan, Nobre, Costa, and Rainey—researchers at Louisiana State University and the University of Coimbra (Coimbra, Portugal).
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Oxygen is also readily detectable in spectra, with multiple bands across a relatively wide wavelength range, therefore it makes a very good biosignature. However, finding oxygen alone in a planet's atmosphere is not enough to confirm a biosignature because of the false positive mechanisms associated with it. One possibility is that oxygen can build up abiotically via photolysis if there is a low inventory of non-condensible gasses or if it loses a lot of water. Finding and distinguishing a biosignature from its potential false positive mechanisms is one of the most complicated parts of testing for viability because it relies on human ingenuity to break an abiotic-biological degeneracy, if nature allows.
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The climate here is classified as an arid desert with low soil nutrients and low diversity of species, because the typical resources that common species need in order to stay alive are not readily available in desert habitat conditions. It is extremely hard for any new non-native species to invade this area and live to reproduce. (However, on the other hand "Because overall levels of soil nutrients in the Mojave Desert are low relative to other ecosystems, the high nutrient concentrations that produce high cover of competitive natives that hinders the establishment and growth of aliens may never be found in this region.") New species are less likely to be able to establish themselves in harsh climate areas, or communities that are abiotically stressful.
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Based on the high concentration of phosphate in the Earth's crust, the universal metabolism of pyrophosphate and polyP in modern cells, the ability to form phosphates abiotically, and its simplicity compared to nucleotides and nucleic acids, replication probably began on phosphate-rich mineral surfaces and involved phosphate related enzymes. Replicases are necessary for the genetic code to have existed, so Cavalier- Smith argues that "polyP kinases and pyrophosphate kinases may have been among the earliest protein-coded catalysts." If these did exist, then polyP-binding proteins would have been the most useful source of energy for the obcells. Due to its anionic properties, it is quite plausible that while immersed in the nucleotide and nucleic acid rich environment, polyP-binding proteins could have polymerized with these substances.
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