1 Introduction. - Extreme Environments. - Environmental Extremes. - Evolutionary Considerations. - References. - 2 The Habitats. - Origins of Thermal Environments. - Constancy of Temperature. - Long-term Constancy. - The Death of Mushroom Spring. - Locations of Hot Springs Studied. - Choosing Springs for Study. - Effect of Temperature on Physical and Chemical Parameters. - Effect of Temperature on Biologically Active Substances. - Chemistry of Hot Springs. - Bimodal pH Distribution of Hot Springs of the World. - Drilling and Subsurface Chemistry. - References. - 3 The Organisms: General Overview. - Temperature and Species Diversity. - Is There an Upper Temperature for Life?. - The Work of Setchell. - Taxonomic Confusion between Blue-green Algae and Nonchlorophyllous Procaryotes (Bacteria). - Well-characterized Thermophilic Procaryotes. - Thermophilic Eucaryotes. - The Upper Temperature Limit for Eucaryotes. - References. - 4 The Genus Thermus. - Isolation Procedures and Habitat. - Morphology of Thermus aquaticus. - Physiological and Nutritional Characteristics. - Thermostable Enzymes of Thermus aquaticus. - Protein Synthesis. - Lipids and Membranes of Thermus aquaticus. - Final Words. - References. - 5 The Genus Thermoplasma. - Characteristics of Thermoplasma. - DNA Base Composition. - Nomenclature. - Habitats of Thermoplasma. - Specific Isolation Procedures for Thermoplasma. - Serological Studies. - Cellular Stability of Thermoplasma. - The Lipids of Thermoplasma. - Membrane Vesicles and Spin Label Studies. - Intracellular pH. - Osmotic Relations of Thermoplasma. - The Nature of the Yeast Extract Requirement. - Nutrition in the Natural Habitat. - Evolution of Thermoplasma. - References. - 6 The Genus Sulfolobus. - Morphology of Sulfolobus. - Nature of the Cell Wall. - Pili and Attachment to Sulfur. - Taxonomy. - Specific Isolation Procedures. - Habitats. - Temperature Relations. - Serology. - Cellular Stability. - Lipids of Sulfolobus. - Sulfur Oxidation. - CO2 Fixation. - Sulfide Oxidation. - Ferrous Iron Oxidation. - Ferric Iron Reduction. - Heterotrophic Nutrition. - Leaching and Oxidation of Sulfide Minerals. - Growth Rates of Sulfolobus in Nature. - Ecology of Sulfolobus in Hot Acid Soils. - Biogeography and Dispersal. - Evolution of Sulfolobus. - References. - 7 The Genus Chloroflexus. - Isolation and Culture of Chloroflexus. - Morphology of Chloroflexus. - Nutritional Studies on Chloroflexus. - Sulfur Metabolism of Chloroflexus. - Pigments of Chloroflexus. - Physiology of CO2 Fixation. - Habitat of Chloroflexus. - Ecology of Chloroflexus in Hot Springs. - Adaptation of Chloroflexus to Various Light Intensities. - Evolutionary Significance of Chloroflexus. - References. - 8 The Thermophilic Blue-green Algae. - Cultivation of Thermophilic Blue-green Algae. - The Genus Mastigocladus. - The Genus Synechococcus. - Light Responses and Adaptation of Thermophilic Blue-green Algae. - The Effect of Wide Temperature Fluctuations on Blue-green Algae. - References. - 9 The Genus Cyanidium. - Culture Isolation and Structure of Cyanidium. - Lipids of Cyanidium. - Pigments and Photosynthesis of Cyanidium. - Habitat of Cyanidium. - Temperature Limits of Cyanidium. - Absence of Temperature Strains in Cyanidium. - Growth Rates of Cyanidium in Nature. - Relationship to pH. - Effect of Light Intensity. - Heterotrophy of Cyanidium: Ecological Significance. - Nitrogen Nutrition of Cyanidium. - Biogeography of Cyanidium. - References. - 10 Life in Boiling Water. - Bacterial Growth Rates above 90C. - Upper Temperature for Life. - Limits of Microbial Existence: Temperature and pH. - The Bacteria of Boulder Spring. - The Bacteria of Octopus Spring. - InRetrospect. - References. - 11 Stromatolites: Yellowstone Analogues. - Siliceous Algal and Bacterial Stromatolites in Hot Springs and Geyser Effluents of Yellowstone National Park. - Controls of Stromatolite Morphogenesis and Lamination Production. - Studies on the Reasons for Node Formation by Phormidium. - Photosynthesis in Intact and Dispersed Nodes. - Bacterial Stromatolites. - References. - 12 A Sour World: Life and Death at Low pH. - Lower pH Limit for Living Organisms. - Lower pH Limit for the Existence of Blue-green Algae. - The Eucaryotic Alga Zygogonium. - Bacteria. - Rate of Sulfuric Acid Production in Yellowstone Solfataras. - References. - 13 The Firehole River. - General Features of the River. - Thermal Regime of the River. - Chemical Alteration of the River. - Biological Effects. - Algal Studies. - Bacterial Studies. - Fish in the Firehole River. - Conclusion. - References. - 14 Some Personal History. - Personnel Involved in Yellowstone Research Project. - Bibliographic Note. - Public Service. - Movies and Television. - The West Yellowstone Laboratory. - The Decision to Quit. Language: English