The halophilic micro-organisms form a highly diverse group of organisms. They present the biochemist/physiologist with interesting questions on the strategies used to cope with high osmotic pressures exerted by hypersaline brines and often have a strong impact on the ecosystems in which they thrive. The first section of the book presents in-depth discussions of the taxonomy, cellular properties, metabolic diversity, pigments, ion metabolism and organic osmotic solutes, properties of halophilic proteins, genetics, and biotechnological uses of halophilic micro-organisms. It then goes on describes the occurrence and functioning of these organisms in the Great Salt Lake, the Dead Sea, solar saltern ponds, alkaline soda lakes, and other hypersaline environments worldwide.