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.
I Taxonomy, Ecology and Phylogeny.- Halophily, Taxonomy, Phylogeny and Nomenclature.- The Microbiota of Saline Lakes of the Vestfold Hills, Antarctica.- Halophilic Organisms and the Environment.- Estimation of the Contribution of Archaebacteria and Eubacteria to the Bacterial Biomass and Activity in Hypersaline Ecosystems: Novel Approaches.- Some Primary and Secondary Metabolites of Hypersaline Microbial Mats and Associated Sediments.- Taxonomy of New Species of Moderately Halophilic Eubacteria.- Phenotypic Characterization of Halophilic Bacteria from Ground Water Sources in the United States.- II Physiology.- Halophiles of All Kinds: What are they up to now, and Where do they come from?.- Mechanism of Chloride Transport in Halophilic Archaebacteria.- Processes of Adaptation of Different Cell—Lines of Dunaliella to Widely Differing Salt Concentrations.- Osmoregulation in Rhizobium meliloti: Control of Glycine Betaine Biosynthesis and Catabolism.- Is the Na+-Activated NADH-Quinone-Acceptor Oxidoreductase in Marine Bacteria and Moderate Halophiles a Primary Electrogenic Na+ Pump?.- Ionic Relations and Polyol Metabolism of Marine Fungi in Relation to their Environment.- Salt Adaptation of Ectothiorhodospira.- Lipoic Acid and Dihydrolipoamide Dehydrogenase in Halophilic Archaeobacteria.- Nitrate Reduction in the Extremely Halophilic Bacteria.- Retinal-Opsin-Dependent Detection of Short-Wavelength Ultraviolet Radiation (UV-B), and Endogenous Bias on Direction of Flagellar Rotation in Tethered Halobacterium halobium Cells.- Steps in the Photosensory Signal Chair of Halobacterium halobium.- Mode of Action of Halocins H4 and H6: Are they Effective against the Adaptation to High Salt Environments?.- Bioenergetics of Halobacterium halobium and of H. marismortui.- The response of Halophilic Bacteria to Heavy Metals.- Biochemical Characterization of Dihydrofolate Reductase of Halobacterium volcanii.- III Composition and Structure.- Polar Lipid Structure, Composition and Biosynthesis in Extremely Halophilic Bacteria.- Variations in the Lipid Composition of Aerobic, Halophilic Archaeobacteria.- Bacterioruberins Reinforce reconstituted Halobacterium Lipid Membranes.- The ‘True’ Intracellular Environment of Moderately Halophilic Eubacteria.- Effects of Salinity on Membrane Lipids and Membrane-Derived Oligosaccharides.- Physiology of Halomonas Elongata in Different NaCI Concentratio..- Do Periplasmic Oligosaccharides Provide a Role in the Osmotic Adaptation of Gram-negative Bacteria?.- IV Molecular Biology and Genetics.- The Ribosomal RNA Operons of Halophilic Archaebacteria.- Bacterio-Opsin Gene Expression in Halobacterium halobium.- The Kinetic of the Genetic Exchange Process in Halobacterium volcanii mating.- Physical Mapping and Gene Transfer Methods for Halobacterium (Halo ferax) volcanii.- Gas Vacuole Genes in Halobacteria.- Insertion Elements Affecting Gas Vacuole Gene Expression in Halobacterium halobium.- Genomic Organization Studies in Halobacteria Using Pulse Field Gel Electrophoresis.- Physical and Genetic Mapping of the Unstable Gas Vesicle Plasmid in Halobacterium halobium NRC-1.- Enzymology and Genetics of an Alpha-like DNA Polymerase from Halobacterium halobium.- Phylogeny of DNA-dependent RNA Polymerases: Testimony for the Origin of Eukaryotes.- DNA Topology in Halobacteria.- V Applied Aspects of Halophilic Organisms.- An Application of a Bioreactor with Flocculated Cells of Halophilic Micrococcus varians Subsp. Halophilus which Preferentially Adsorbed Halophilic Nuclease H to 5’-Nucleotide Production.- Novel Compatible Solutes and their Potential Application as Stabilizers in Enzyme Technology.- Lysis of Halobacteria with Bile Acids and Proteolytic Enzymes of Halophilic Archaeobacteria.- An Archaeobacterial Antigen Used to Study Immunological Humoral Response to C-myc Oncogene Product.- Biopolymer Production by Haloferax mediterranei.- Halophiles in Thai Fish Sauce (Nam Pla).- Liquid Fuel (Oil) from Halophilic Algae: A Renewable Source of Non-Polluting Energy.