From 1965 through 1975, I conducted an extensive field and laboratory research project on thermophilic microorganisms. The field work was based primarily in Yellowstone National Park, using a field laboratory we set up in the city of W. Yellowstone, Montana. The laboratory work was carried out from 1965 through 1971 at Indiana University, Bloomington, and subsequently at the University of Wisconsin, Madison. Although this research project began small, it quickly ramified in a wide variety of directions. The major thrust was an attempt to understand the ecology and evolutionary relationships of thermophilic microorganisms, but research also was done on biochemical, physiologic, and taxonomic aspects of thermophiles. Four new genera of thermophilic microorganisms have been discovered during the course of this 10-year period, three in my laboratory. In addition, a large amount of new information has been obtained on some thermophilic microorganisms that previously had been known. In later years, a considerable amount of work was done on Yellowstone algal bacterial mats as models for Precambrian stromatolites. In the broadest sense, the work could be considered geomicrobiological, or biogeochemi cal, and despite the extensive laboratory research carried out, the work was always firmly rooted in an attempt to understand thermophilic microorga nisms in their natural environments. Indeed, one of the prime motivations for initiating this work was a view that extreme environments would provide useful models for studying the ecology of microorganisms. As a result of this 10-year research project, I published over 100 papers.

Inhalt
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 90°C.- 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.