During recent years the subject of extreme environments and extremophiles has become a central topic in modern Biology. The capability of some microorganisms to withstand, and often prefer, the harsh conditions found in such environments is helping to define the physicho-chemicallimits of life and in consequence its essential nature. Halophiles are one of the most representative types of extremophiles, requiring high concentrations of inorganic salts, mostly sodium chloride, to grow and survive. They inhabit hypersaline environments, the distribution and abundance of which dur ing geological eras are attested by the vast amounts of evaporite rocks present in the Earth crust and by their role in the generation of petroleum deposits. The corditions of high osmolarity and ionic strength that are concomitant with concentrated salt solutions challenge the stability of lipid bilayers and the structure of proteins forcing halophilic microbes to develop specialized molecules and physiological me;;hanisms to cope with this environmental stress. Even so, halophilism is a widespread trait in the microbial world. All the major groups of eucaryotic microbes, two groups of archaeobacteria and most phylogenetic branches of eubacteria have halophilic representatives. Therefore, the study of halophilic microorganisms is indeed a highly heterogeneous and extense topic. The present volume contains the contributions to the FEMS-NATO Advanced Research Workshop on "General and Applied Aspects of Halophilic Microorganisms" held at Alicante, Spain, September 17-22, 1989.

"This water" he told me, "runs out to the eastern region, and flows into the Arabah; and when it comes into the sea, into the sea of foul waters [i. e. , the Dead Sea], the water will become wholesome. Every living creature that swarms will be able to live wherever this stream goes; the fish will be very abundant once these waters have reached there. It will be wholesome, and everything will live wherever this stream goes. Fishermen shall stand beside it all the way from En-gedi to En-eglaim; it shall be a place for drying nets; and the fish will be of various kinds [and] most plentiful, like the fish of the Great Sea. " Ezekiel’s prophecy (Ezekiel 47: 8-10) for revival and purification of the Dead Sea waters This new book on "Halophilic Microorganisms and their Environments" is the fifth volume in the COLE series (Cellular Origin and Life in Extreme Habitats (see: http://www. wkap. nl/prod/s/COLE). In the previous books we covered aspects of enigmatic microorganisms, microbial diversity, astrobiology, and symbiosis, so this book on halophilic microbes adds a fitting link to the rest of series' books. Since ancient times hypersaline habitats have been considered extreme environments, and some were thought not to sustain life at all. Yet, every organism requires salt for its existence. Salty places have been compared to an environment of extinction (e. g. , the Dead Sea).

Various groups of microorganisms - bacteria, archaea, algae and even fungi - have adapted to a life in a hypersaline environment. Halophilic Microorganisms explores the many-fold aspects of life under these extreme conditions. Several contributions analyze the microbial communities in different hypersaline environments such as salterns, soda lakes, and the Dead Sea or salt sediments. Reviews of their biodiversity, phylogeny, and genetics are given as well as of the diverse adaptation strategies of salt-tolerant or salt-requiring microorganisms. Microorganisms that have adapted to moderate salt concentrations or to habitats with drastic fluctuations are also treated in addition to the extreme halophiles. Their physiological, biochemical and molecular mechanisms developed in response to salinity and high osmotic pressure as well as current and future biotechnological applications are presented.

The world of halophiles is quite diverse and their representatives in three domains of life i.e. archaea, bacteria and eukarya. They are found all over the small subunit rRNA based tree of life and these micro-organisms are adapted to salt concentration up to saturation hence able to grow at >300g/l Nacl concentration. Their metabolic diversity is high as well encompassing oxygenic and anoxygenic phototrophs, aerobic heterotrophs, denitrifiers, sulphate reducers, fermenters and methanogens. The proteins of halophiles are magnificently engineered to function in a milieu containing 2-5M salt that encodes genes represent a valuable repository and resource for reconstruction and visualizing processes of habitat selection and adaptive evolution. Search for new enzymes endowed with novel activities and enhanced stability continues to be desirable purpose for important commercial production of biotechnological significance. These poly extremophiles proved excellent source of enzymes and metabolites possessing inherent ability to function in extreme conditions of high salt, alkaline pH and facilitating catalysis for industrial application in food processing, industrial bioconversion, bioremediation etc. In fact, it has just begun to realize the great potential and true extent of diversity and suitable applications if explored them judiciously. This book highlights current applications and research on halophiles to provide a timely overview. Chapters are written by expert authors from around the world and include topics of varied importance which include their role to play in enzyme production, restoration of soil fertility and plant growth , antimicrobial and biocatalytic potential, biomolecules in nanotechnology and aspects of quorum sensing. The book is divided into three sections, dealing with biodiversity, biotechnology and sustainable exploitation of halophiles. This major new work represents a valuable source of information to all those scientists interested in microorganisms in general and extremophiles in particular with respect to their innovative products and applications.

This book bridges a gap in the literature by bringing together leading specialists from different backgrounds. It addresses the specific need for a readable book on this very interdisciplinary and new topic at research level.

This book presents the latest results in the exploration of halophilic bacteria, archaea, fungi and viruses. Basic and molecular aspects as well as possible biotechnological applications of halophiles are highlighted by leading scientists. Topics include: the family Halomonadaceae; the hypersaline lakes of Inner Mongolia ; Salinibacter ruber - from genomics to microevolution and ecology; the impact of lipidomics on the microbial world of hypersaline environments; molecular mechanisms of adaptation to high salt concentration in the black yeast Hortaea werneckii; viruses in hypersaline environments; initiation and regulation of translation in halophilic Archaea; protein transport into and across haloarchaeal cytoplasmic membranes; protein glycosylation in Haloferax volcanii; the effect of anoxic conditions and temperature on gas vesicle formation in Halobacterium salinarum; halophiles exposed to multiple stressors; cellular adjustments of Bacillus subtilis to fluctuating salinities; the nature and function of carotenoids in Halobacillus halophilus; xanthorhodopsin; enzymatic biomass degradation by halophilic microorganisms; and enzymes from halophilic Archaea.