Ebook Physiology and biochemistry of extremophiles: Part 2
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Ebook Physiology and biochemistry of extremophiles: Part 2
IV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2aline EnvironmentsAharon OrenINTRODUCTIONAbout 70% of the surface of planet Earth is covered by seawater: a salty environment that contains approximately 35 g of total dissolved salts per liter, 78% of which is NaCI. Although many microorganisms are unable to cope with life at seawater salinity, the Ebook Physiology and biochemistry of extremophiles: Part 2 marine environment cannot be considered extreme”: the seas arc populated by a tremendous diversity of micro- and macroorganisms, ar least as diverseEbook Physiology and biochemistry of extremophiles: Part 2
as the world of freshwater organisms.However, there are also environments with salt concentrations much higher than those found in the sea. When salt IV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2other hand, highly salt-tolerant and often even highly salt-requiring microorganisms can lie found up to the highest salt concentrations: NaCI-saturated brines that contain salt concentrations of over 300 g/litcr. Halophilic Archaea, Bacteria, and eukaryotic unicellular algae live in the Dead Sea, i Ebook Physiology and biochemistry of extremophiles: Part 2n the Great Salt l ake, in saltern crystallizer ponds, and in other salt-saturated environments, and they often reach high densities in such environmeEbook Physiology and biochemistry of extremophiles: Part 2
nts.This chapter explores the world of high salt environments worldwide and the diversity of microorganisms that inhabit these environments.DIVERSITY IV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2al compositions, artificial salt lakes such as solar salterns for rhe production ofNaCl from seawater, underground deposits of rock salt, as well as salted food products, highly saline soils, and others (Javor, 1989; Oren, 2002a).rhe two largest truly hypcrsaline inland salt lakes arc the Great Salt Ebook Physiology and biochemistry of extremophiles: Part 2 Lake, Utah, and the Dead Sea. 1 he Great Salt Lake, a remnant of the ice-age saline Lake Bonneville that has largely dried out, has a salt compositioEbook Physiology and biochemistry of extremophiles: Part 2
n that resembles that of seawater (“thalas-sohalinc” brines). Owing to climatic changes and to human interference (division of the lake into a northerIV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2ntury. The northern basin is nowadays saturated with respect to NaCl. It is unfortunate that we know so little about the microbiology of the Great Salt Lake: after the pioneering studies by Fred Post in the 1970s (Post, 1977), the study of the microbial communities in the lake has been sadly neglect Ebook Physiology and biochemistry of extremophiles: Part 2ed. I lowever, a recent renewed interest in the biology of the lake is expected to change the picture, so that we soon may expect to get a much betterEbook Physiology and biochemistry of extremophiles: Part 2
picture ol the diversity of microorganisms in the largest of all hypersaline lakes, their properties, and their dynamics (Baxter et al., 200.5).rhe DIV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2atly different from that of seawater. Magnesium, not sodium, is the dominant cation, calcium is present as well in very high concentrations, and the pH is relatively low: around 6, as compared with 7.5 to s in thalassohalinc brines. Indeed, the present-day Dead Sea is a remnant of the Pleistocene La Ebook Physiology and biochemistry of extremophiles: Part 2ke l.isan, whose salts were of marine origin, but massive precipitation of halite and other geological phenomena have greatly changed the chemical proEbook Physiology and biochemistry of extremophiles: Part 2
perties of the brine. Yet, a few types of microorganisms can survive even in theA. Oren • I he Institute of Life Sciences and the Moshe Shilo Minerva IV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2e in salt concentration and relative increase in divalent cation concentrations in the past decades have made the Dead Sea environment too extreme for massive development of even the most salt-adapted microorganisms. Only when the lipper water layers become diluted as a result of winter rain floods Ebook Physiology and biochemistry of extremophiles: Part 2do dense microbial communities develop in the lake. A 10 to 15% dilution is sufficient to trigger massive blooms of the green alga Dunaliella and diffEbook Physiology and biochemistry of extremophiles: Part 2
erent types of red halophilic Archaea (Oren, 1988, 1999a).Other natural hypersaline lakes arc highly alkaline. Mono Lake, California (total salt conceIV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2can Rift Valley such as l ake Magadi, Kenya, as well as the lakes of Wadi Natrun, Egypt, and some soda lakes in China; here dense communities of halophilic Archaea and other prokaryotes are found in salt-saturated brines al pH values above 10. This illustrates that some halophilic microorganisms arc Ebook Physiology and biochemistry of extremophiles: Part 2 true “polycxtrcmophilcs” (Rothschild and Mancinclli, 2001), organisms that can simultaneously cope with more than one type ol environmental stress. TEbook Physiology and biochemistry of extremophiles: Part 2
he discovery ol a truly thermophilic halophile, ỉỉalo-thermothrix ore/ni, isolated from a salt lake in Tunisia, shows that also life ar high temperatuIV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2 at temperatures up to 68°c (optimum 60°C) (Cayol el al., 1994).Coastal solar salterns, found worldwide in dry-tropical and subtropical climates, arc man-made, rha-lassohalinc hypcrsalinc environments in which seawater is evaporated lor the production OỈ salt. Such saltern systems are operated as a Ebook Physiology and biochemistry of extremophiles: Part 2series ol ponds ol increasing salinity-, enabling controlled sequential precipitation of different minerals (calcite, gypsum, and halite). As a resultEbook Physiology and biochemistry of extremophiles: Part 2
, these saltern ecosystems present US with a more or less stable gradient of salt concentrations, from seawater salinity to NaCI precipitation and beyIV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2unities generally develop both in the water and in the surface sediments of the saltern ponds (Oren, 2005). It is therefore not surprising that these saltern ecosystems have become popular objects for the study of microbial biodiversity and community dynamics at high salt concentrations, and much of Ebook Physiology and biochemistry of extremophiles: Part 2 our understanding of the biology of halophilic microorganisms is based on studies of the saltern environment and in-depth studies of microorganisms iEbook Physiology and biochemistry of extremophiles: Part 2
solated from such salterns.Another hypersaline aquatic habitat that appears to harbor interesting communities of halophilicmicroorganisms is the highlIV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2ily accessible for sampling, little is known thus far on their microbiology. 1 lowever, a preliminary exploration of such brines from the bottom of the Red Sea, using culture-independent techniques, yielded evidence for the presence of a wealth of novel ry-pes of halophiles (Eder el al., 1999). A co Ebook Physiology and biochemistry of extremophiles: Part 2mprehensive multidisciplinary research program was recently launched, aimed at the elucidation of the biology of the deep-sea hypcrsaline anoxic basinEbook Physiology and biochemistry of extremophiles: Part 2
s in the Eastern Mediterranean Sea. rhe first published data that emerged from this program (van der Widen el al., 2005) prove that we may expect manyIV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2lated to their chemical and physical properties, can be found in a recent monograph (Oren, 2002a).Ilalophilic and halololerant microorganisms are not only found in aquatic habitats. They can be recovered from many other environments in which high salt concentrations and/or low water activities occur Ebook Physiology and biochemistry of extremophiles: Part 2. Halophilic and highly halotolerant bacteria can easily be recovered from saline soils. Some plants that grow on saline soils in arid areas activelyEbook Physiology and biochemistry of extremophiles: Part 2
excrete salt from their leaves, and the phylloplane of these plants thus appeared to be an interesting novel environment lor halophiles (Simon el al.,IV. HALOPHILESPbỵĩáiiug)-Md tiiưiti-Miiln uf Edited by c Gcniiv ind N. Gljnidwtt o 2007 ASM Presfc, Wuhinglco, D.c.Chapter 17Biodiversity in Highly Sa Ebook Physiology and biochemistry of extremophiles: Part 2n be an excellent growth substrate for halophilic or halotolerant microorganisms. In tact, the production of some traditionally fermented food products in the Far East is based on rhe activity of halophilic bacteria.Maybe rhe most surprising environment in which halophilic microorganisms have been f Ebook Physiology and biochemistry of extremophiles: Part 2ound is the rock salt deposits found in many places worldwide. Live bacteria (endospore-forming organisms of the genus Bacillus) have even been recoveEbook Physiology and biochemistry of extremophiles: Part 2
red from rock salt crystals that had been buried for 250 million years (Vrecland et al., 2000), while viable Archaea of the family Ilalobacleriaceae oGọi ngay
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