Hydrothermal vent high temperature

Another methanogen, Methanococcus jannaschii, isolated from a deep-sea hydrothermal vent at temperatures of 85 C or higher, has membrane lipids based on cyc-archaeol (1C), which was not found in any other species of methanogens surveyed and may be unique to methanogens from deep-sea hydrothermal vents [34,67]. It is possible that the presence of cyc-archaeol-based lipids may be related to the high pressures under which these deep-sea methanogens live. 

The flow of hydrothermal solutions iato the oceans from hydrothermal vents, ie, springs coming from the sea floor ia areas of active volcanism, and the chemical reactions occurring there by high temperature alteration of basalts ate of significance ia the mass balance of and. Eurthermore,... 

Michard, A. and Albarede, F., Michard, G., Minsten, J.F. and Charlou, J.L. (1983) Rare-earth elements and uranium in high-temperature solutions from East Pacific Rise hydrothermal vent field (I3°N). Nature (London), 303, 795-797. 

The same problem, the stability of the nucleobases, was taken up by Levi and Miller (1998). They wanted to show that a synthesis of these compounds at high temperatures is unrealistic, and thus they took a critical look at the high temperature biogenesis theories, such as the formation of biomolecules at hydrothermal vents (see Sect. 7.2). The half-life of adenine and guanine at 373 K is about a year, that of uracil about 12 years and of the labile cytosine only 19 days. Such temperatures could have easily been reached when planetoids impacted the primeval ocean. 

In the same year, Miller and the biologist Antonio Lazcano (National Autonomous University of Mexico) spoke out against hypotheses that life could have originated at hydrothermal vents. They believe that the presence of thermophilic bacteria (the oldest life forms) does not prove that biogenesis occurred in the depths of the oceans. Stanley Miller sees a greater chance for successful pre-biotic chemistry under the conditions of a cold primeval Earth rather than at high temperatures in hydrothermal regions (Miller and Lazcano, 1995). 

The processes occurring at hydrothermal systems in prebiotic periods were without doubt highly complex, as was the chemistry of such systems this is due to the different gradients, for example, of pH or temperature, present near hydrothermal vents. Studies of the behaviour of amino acids under simulated hydrothermal conditions showed that d- and L-alanine molecules were racemised at different rates the process was clearly concentration-dependent. L-Alanine showed a low enantiomeric excess (ee) over D-alanine at increasing alanine concentrations. The same effect was observed with metal ions such as Zn2+ in the amino acid solution. Thus, homochi-ral enrichment of biomolecules in the primeval ocean could have resulted under the conditions present in hydrothermal systems (Nemoto et al., 2005). 

Lithium is enriched in high temperature (c. 350°C) vent fluids by a factor of 20-50 relative to seawater (Edmond et al. 1979 Von Damm 1995). The Li isotopic compositions of marine hydrothermal vent fluids ranged from MORB-like to heavier compositions (see... 

In high-temperature hydrothermal systems, sulfide-oxidizing bacteria are responsible for most of the primary production supporting the vent community. As shown in Eq. 19.7,... 

In comparison to the high-temperature hydrothermal vents, biomass at the Lost City vent field is much lower and the macrofauna are much smaller, typically less than 100 pm. These macrofeuna are predominantly gastropods and polychaetes with 58% of the species being endemic, including nine new species of crustaceans ... 

The chemicals come from cracks on the ocean floor called hydrothermal vents. Hydrothermal vents are most often found where the sea floor is spreading due to the movement of sections of Earths crust. Seawater enters the cracks produced by the spreading plates and is heated by hot magma lying under the surface. The water can reach temperatures as high as 750°F (400°C). 

There are three environments on Earth where microbes have been identified with temperature tolerances in a range of 100°C to 121 °C, namely, submarine hydrothermal vents, the subterranean deep biosphere, and terrestrial hot springs (Table 4.1). The highest temperature tolerances (110-121 °C) are found in microbes from marine hydrothermal vents and the subterranean deep biosphere high pressures prevent these waters from boiling at 100 °C, the normal boiling point of water at 1.01 bar (1 atm) pressure. From terrestrial hot springs, microbes have been isolated that can tolerate temperatures up to 103°C (Table 4.1). 

Baross, J.A., and Deming, J.W. 1998. Growth at high temperatures Isolation and taxonomy, physiology, and ecology. Pp. 169-217 in The Microbiology of Deep-Sea Hydrothermal Vents (D.M. Karl, ed.). CRC Press, Boca Raton, Fla. 

Figure 7.23. Effects of temperature on mitochondrial function. (Upper panel). Arrhenius plot illustrating the slope discontinuity ( break ) that commonly occurs at a high temperature of measurement, the Arrhenius break temperature (ABT). Data are for mitochondria of the hydrothermal vent tubeworm Riftia pachyptila (after Dahlhoff et al., 1991). (Lower panel) Arrhenius break temperatures for mitochondrial respiration of diverse invertebrates and fishes. The open square is for mitochondrial respiration of the Antarctic nototheniid fish Trematomus bernacchii and is not included in the regression analysis. A line of identify (ABT = adaptation temperature) is also shown (see text for analysis). (Data from Dahlhoff and Somero, 1993b Dahlhoff et ah, 1991 Weinstein and Somero, 1998.)...

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