Part 2 book “Physiology and biochemistry of extremophiles” has contents: Biodiversity in highly saline environments, molecular adaptation to high salt, physiology and ecology of acidophilic microorganisms, molecular adaptation to high salt, bioenergetic adaptations that support alkaliphily, environmental and taxonomic biodiversities of gram-positive alkaliphiles, and other contents. | IV. HALOPHILES This page intentionally left blank Physiology and Biochemistry of Extremophiles Edited by C. Gerday and N. Glansdorff © 2007 ASM Press, Washington, . Chapter 17 Biodiversity in Highly Saline Environments AHARON OREN NaCl from seawater, underground deposits of rock salt, as well as salted food products, highly saline soils, and others (Javor, 1989; Oren, 2002a). The two largest truly hypersaline inland salt lakes are the Great Salt Lake, Utah, and the Dead Sea. The Great Salt Lake, a remnant of the ice-age saline Lake Bonneville that has largely dried out, has a salt composition that resembles that of seawater (“thalassohaline” brines). Owing to climatic changes and to human interference (division of the lake into a northern and a southern basin by a rockfill railroad causeway in the 1950s), the salinity of the lake has been subject to strong fluctuations in the past century. 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 neglected. However, 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 better picture of the diversity of microorganisms in the largest of all hypersaline lakes, their properties, and their dynamics (Baxter et al., 2005). The Dead Sea, with its present-day salt concentration of over 340 g/liter, is an example of an “athalassohaline” brine, which has an ionic composition greatly 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 to 8 in thalassohaline brines. Indeed, the present-day Dead Sea is a remnant of the Pleistocene Lake Lisan, whose salts were of marine origin, but
