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Chlorobactane
Chlorobactane is the diagenetic product of an aromatic carotenoid produced uniquely by green-pigmented green sulfur bacteria (GSB) in the order ''Chlorobiales''. Observed in organic matter as far back as the Paleoproterozoic, its identity as a diagnostic biomarker has been used to interpret ancient environments. Background Chlorobactene is a monocyclic accessory pigment used by green sulfur bacteria to capture electrons from wavelengths in the visible light spectrum. Green sulfur bacteria (GSB) live in anaerobic and sulfidic ( euxinic) zones in the presence of light, so they are found most often in meromictic lakes and ponds, sediments, and certain regions of the Black Sea.Imhoff, Johannes F. (1995). “Taxonomy and Physiology of Phototrophic Purple Bacteria and Green Sulfur Bacteria”. Anoxygenic Photosynthetic Bacteria, pp 1 – 15. Kluwer Academic Publishers. The enzyme CrtU converts γ-carotene into chlorobactene by shifting the C17 methyl group from the C1 site to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Okenane
Okenane, the diagenetic end product of okenone, is a biomarker for Chromatiaceae, the purple sulfur bacteria. These anoxygenic phototrophs use light for energy and sulfide as their electron donor and sulfur source. Discovery of okenane in marine sediments implies a past euxinic environment, where water columns were anoxic and sulfidic. This is potentially tremendously important for reconstructing past oceanic conditions, but so far okenane has only been identified in one Paleoproterozoic (1.6 billion years old) rock sample from Northern Australia. Background Okenone is a carotenoid, a class of pigments ubiquitous across photosynthetic organisms. These conjugated molecules act as accessories in the light harvesting complex. Over 600 carotenoids are known, each with a variety of functional groups that alter their absorption spectrum. Okenone appears to be best adapted to the yellow-green transition (520 nm) of the visible spectrum, capturing light below marine pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Okenane
Okenane, the diagenetic end product of okenone, is a biomarker for Chromatiaceae, the purple sulfur bacteria. These anoxygenic phototrophs use light for energy and sulfide as their electron donor and sulfur source. Discovery of okenane in marine sediments implies a past euxinic environment, where water columns were anoxic and sulfidic. This is potentially tremendously important for reconstructing past oceanic conditions, but so far okenane has only been identified in one Paleoproterozoic (1.6 billion years old) rock sample from Northern Australia. Background Okenone is a carotenoid, a class of pigments ubiquitous across photosynthetic organisms. These conjugated molecules act as accessories in the light harvesting complex. Over 600 carotenoids are known, each with a variety of functional groups that alter their absorption spectrum. Okenone appears to be best adapted to the yellow-green transition (520 nm) of the visible spectrum, capturing light below marine pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euxinia
Euxinia or euxinic conditions occur when water is both anoxic and sulfidic. This means that there is no oxygen (O2) and a raised level of free hydrogen sulfide (H2S). Euxinic bodies of water are frequently strongly stratified, have an oxic, highly productive, thin surface layer, and have anoxic, sulfidic bottom water. The word euxinia is derived from the Greek name for the Black Sea (Εὔξεινος Πόντος (''Euxeinos Pontos'')) which translates to "hospitable sea". Euxinic deep water is a key component of the Canfield ocean, a model of oceans during the Proterozoic period (known as the Boring Billion) proposed by Donald Canfield, an American geologist, in 1998. There is still debate within the scientific community on both the duration and frequency of euxinic conditions in the ancient oceans. Euxinia is relatively rare in modern bodies of water, but does still happen in places like the Black Sea and certain fjords. Background Euxinia most frequently occurred in the Eart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meromictic Lake
A meromictic lake is a lake which has layers of water that do not intermix. In ordinary, holomictic lakes, at least once each year, there is a physical mixing of the surface and the deep waters. The term ''meromictic'' was coined by the Austrian Ingo Findenegg in 1935, apparently based on the older word ''holomictic''. The concepts and terminology used in describing meromictic lakes were essentially complete following some additions by G. Evelyn Hutchinson in 1937. Characteristics Most lakes are ''holomictic''; that is, at least once per year, physical mixing occurs between the surface and the deep waters. In so-called monomictic lakes, the mixing occurs once per year; in dimictic lakes, the mixing occurs twice a year (typically spring and autumn), and in polymictic lakes, the mixing occurs several times a year. In meromictic lakes, however, the layers of the lake water can remain unmixed for years, decades, or centuries. Meromictic lakes can usually be divided into th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carotenoid
Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, and Fungus, fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, maize, corn, tomatoes, Domestic Canary, canaries, flamingos, salmon, lobster, shrimp, and daffodils. Carotenoids can be produced from Lipid, fats and other basic organic metabolic building blocks by all these organisms. It is also produced by Endosymbiont, endosymbiotic bacteria in Whitefly, whiteflies. Carotenoids from the diet are stored in the fatty tissues of animals, and exclusively Carnivore, carnivorous animals obtain the compounds from animal fat. In the human diet, Small intestine#Absorption, absorption of carotenoids is improved when consumed with fat in a meal. Cooking carotenoid-containing vegetables in oil and shredding the vegetable both increase carotenoid bioavailability. There are over 1,100 known c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kerogen
Kerogen is solid, insoluble organic matter in sedimentary rocks. Comprising an estimated 1016 tons of carbon, it is the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. It is insoluble in normal organic solvents and it does not have a specific chemical formula. Upon heating, kerogen converts in part to liquid and gaseous hydrocarbons. Petroleum and natural gas form from kerogen. Kerogen may be classified by its origin: lacustrine (e.g., algal), marine (e.g., planktonic), and terrestrial (e.g., pollen and spores). The name "kerogen" was introduced by the Scottish organic chemist Alexander Crum Brown in 1906,''Oxford English Dictionary'' 3rd Ed. (2003) derived from the Greek for "wax birth" (Greek: κηρός "wax" and -gen, γένεση "birth"). The increased production of hydrocarbons from shale has motivated a revival of research into the composition, structure, and properties of kerogen. Many studies have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Purple Sulfur Bacteria
The purple sulfur bacteria (PSB) are part of a group of Pseudomonadota capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic, and are often found in stratified water environments including hot springs, stagnant water bodies, as well as microbial mats in intertidal zones.Hunter, C.N., Daldal, F., Thurnauer, M.C., Beatty, J.T"The Purple Phototropic Bacteria" '' Springer-Dordrecht'', 2008. Unlike plants, algae, and cyanobacteria, purple sulfur bacteria do not use water as their reducing agent, and therefore do not produce oxygen. Instead, they can use sulfur in the form of sulfide, or thiosulfate (as well, some species can use H2, Fe2+, or NO2−) as the electron donor in their photosynthetic pathways. The sulfur is oxidized to produce granules of elemental sulfur. This, in turn, may be oxidized to form sulfuric acid. The purple sulfur bacteria are largely divided into two families, the Chromatiaceae and the Ectothiorhodospirac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isorenieratene
Isorenieratene is a carotenoid light harvesting pigment with the chemical formula C40H48. Isorenieratene and its derivatives are useful to marine chemists studying the carbon cycle as biomarkers that indicate photic zone anoxia. Isorenieratene is produced by green sulfur bacteria (''Chlorobium'') which perform photosynthesis using hydrogen sulfide rather than water: :H2S + CO2 → SO42− + organic compounds Such anoxygenic photosynthesis requires reduced sulfur (and therefore strictly anaerobic conditions) and light (''hν''). This combination of conditions is very unusual nowadays, since it requires very stratified water columns to achieve a sharp density gradient, i.e. a constrained basin with fresh water flowing, or warm water on top of cooler water. Green sulfur bacteria are commonly found in meromictic lakes and ponds, sediments, and some sinkholes. Some marine environments, such as certain fjords and the Black Sea also fulfill these criteria. In the early history o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diagenetic
Diagenesis () is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a role as sediments become buried much deeper in the Earth's crust. In the early stages, the transformation of poorly consolidated sediments into sedimentary rock (lithification) is simply accompanied by a reduction in porosity and water expulsion (clay sediments), while their main mineralogical assemblages remain unaltered. As the rock is carried deeper by further deposition above, its organic content is progressively transformed into kerogens and bitumens. The process of diagenesis excludes surface alteration (weathering) and deep metamorphism. There is no sharp boundary between diagenesis and metamorphism, but the latter occurs at higher temperatures and pressures. Hydrothermal solutions, meteoric groundwater, rock porosity, permeability, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aromatic
In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to saturated compounds having single bonds, and other geometric or connective non-cyclic arrangements with the same set of atoms. Aromatic rings are very stable and do not break apart easily. Organic compounds that are not aromatic are classified as aliphatic compounds—they might be cyclic, but only aromatic rings have enhanced stability. The term ''aromaticity'' with this meaning is historically related to the concept of having an aroma, but is a distinct property from that meaning. Since the most common aromatic compounds are derivatives of benzene (an aromatic hydrocarbon common in petroleum and its distillates), the word ''aromatic'' occasionally refers informally to benzene derivatives, and so it was first defined. Nevertheless, many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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