Deep sea vents

Holm and Andersson have provided an up-to-date survey of simulation experiments on the synthesis under hydrothermal conditions of molecules important for biogenesis (Holm and Andersson, 2005). It is clear that several research groups have been able to show in the meantime, using simulation experiments, that the conditions present at deep sea vents appear suitable for the synthesis of very different groups of substances. However, it remains unclear how these compounds could have been stabilized and protected against rapid decomposition. At present, metal ions (as complexing agents) and mineral surfaces are the subject of discussion and experiment. 

We also know that a considerable enrichment of prebiotic moieties may have come from submarine vents and other hydrothermal sources (see, for example, Miller and Bada, 1988 Holm and Andersson, 1998 Stetter, 1998). Let s start with the 1979 discovery of deep-sea vents with black smokers, which are associated with an extraordinary abundance of the most phylogenetically primitive organisms on Earth. This ecosystem is sulphur based, and is distinct from the more familiar, photosynthetically-based ecosystem that dominates Earth s surface. Corliss et al. (1981) were struck by the richness of the vent biota, based on chemosynthesis, and proposed that these were the origin of life. 

Life depends on chemical reactions. Chemical reactions take place when plants and animals grow, digest their food, and even when they rest. Some of the chemical reactions that occur in nature take place in the most extreme conditions on the planet, such as near deep-sea vents or in Antarctica. Some reactions are so complex that scientists are not yet sure how they happen. 

Most of the deep, deep ocean has little life in it because it is too cold, only a few degrees above freezing, and, with no sunlight, there is no food to support life. But the area around these deep-sea vents... 

Around deep-sea vents lives a very interesting species of animal the tubeworm. Some tubeworms can grow to be almost 8 feet (3 m) long. They were first discovered in the 1970s around some hydrothermal vents near the Galapagos Islands off the coast of South America. Since then many tubeworms have been found at deep-sea vents all over the world. 

Fisher, C.R. (1996). Ecophysiology of primary production at deep-sea vents and seeps. Biosystematics and Ecology Series 11,313-336. 

Nelson DC, Fisher CR. Chemoautotrophic and methanotrophic endosymbiotic bacteria at deep-sea vents and seeps. In Microbiology of Deep Sea Hydrothermal Vents. Karl DM, ed. 1995. CRC Press Inc., Boca Raton, FL. pp. 125-167. 

Ultimately all chemoautotrophs depend on a nonequilibrium redox gradient, without which there is no thermodynamic driver for carbon fixation. For example, the reaction involving the oxidation of H2S by microbes in deep-sea vents described above is ultimately coupled to oxygen... 

Deep-sea vents have only been studied in the late twentieth century, so there is still much to learn in terms of their global contribution because of their inaccessibility. However, they can affect global fluxes, and some estimates would suggest that warm ridge-flank sites may remove each year, as much as 35% of the riverine flux of sulfur to the oceans (Wheat and Mottl, 2000). The hydrothermal vents are locally important sources of sulfide-containing materials. The black smokers yield polymetal sulfides, that will... 

The discovery of deep-sea vents has led to speculation that they could be involved in the origin of life and here a unique sulfur chemistry... 

The low concentrations of hydrogen sulfide found in the marine atmosphere suggest that there might be a significant flux of the gas from the oceans, but most studies conclude that it is a rather insignificant flux (Shooter, 1999). There is also the potential for the sulfate reduction to occur on particles in the ocean (Cutter and Krahforst, 1988) and some may arise from deep-sea vents, but this source is restricted to water close to the vent (Shooter, 1999). 

However, some scientists believe that the young Earth was too inhospitable a place for life to have developed on its surface at all lacking O2, the atmosphere would also have lacked its present-day stratospheric layer of ozone (O3), which screens large quantities of harmful ultraviolet radiation from the surface. They believe that a more likely environment for abiogenesis (life from prelife) was in the vicinity of deep-sea vents, holes in the crust under the ocean from which hot, mineral-laden water flows. 

Extremophilic microbes (extremophiles) abound in extreme habitats, such as acidophiles (acidic sulfurous hot springs), alkalophiles (alkaline lakes), halophiles (salt lakes), piezo (baro)- and (hyper)thermophiles (deep-sea vents), ° and... 

Iwata S, Ostermeier C, Ludwig B, Michel H (1995) Structure at 2.8A resolution of cytochrome c oxidase from Paracoccus denitrificans. Nature 376 660-669 Jannasch HW, Nelson DC, Wirsen CO (1989) Massive natural occurrence of unusually large bacteria (Beggiatoa sp.) at a hydrothermal deep-sea vent site. Nature 342 834—836 Jetten MSM, de Bruijn P, Kuenen JG (1997) Hydroxylamine metabolism in Pseudomonas PB16 involvement of a novel hydroxylamine oxidoreductase. Antonie van Leeuwenhoek. 71 69-74... 

Only deep-sea hydrothermal vents and cold-seeps are discussed in this chapter. Shallow vents and seeps are known from a variety of locations, from the littoral zone to several tens of metres (e.g. Holm, 1987 Jensen etal., 1992 Dando etal., 1994a,b, 1995). Shallow vents have many differences from their deeper counterparts. They lack metal-rich and extreme high temperature fluids, as well as large-scale mineral deposits. They also lack typical hydrothermal vent animals. Biomass production in both systems is lower than at deep-sea vents and deep... 

The earth is rich in hostile environments. These include a wide array of natural systems deep-sea vents, salt brines, thermal pools, volcanic lakes, and frigid ice fields. Others are anthropogenic, often the result of extractive hard rock, oil or coal mining. Nobel laureate Paul Crutzen suggested that we are currently living in the anthropocene , an era in which humans and human activities have become a major geological force on the planet [11]. Whether man-made or natural, extreme environments can harbor life forms called extremophiles. 

Bacteriologist Thomas Brock demonstrated the importance of extremophiles in the 1960 s when he isolated bacteria from a 70°C thermal pool in Yellowstone National Park. In the forty years following Brock s discovery, scientists have explored ecological niches as varied as deep sea vents and Antarctic ice sheets and have also found unusual life forms in unexpected places [12]. 

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