Diversity of the Heme-Copper Superfamily in Archaea: Insights from Genomics and Structural Modeling -- Structure of Photosystems I and II -- Microbial Rhodopsins: Scaffolds for Ion Pumps, Channels, and Sensors -- Life Close to the Thermodynamic Limit: How Methanogenic Archaea Conserve Energy -- ATP Synthesis by Decarboxylation Phosphorylation -- The Three Families of Respiratory NADH Dehydrogenases -- Hydrogenases and H+-Reduction in Primary Energy Conservation -- A Structural Perspective on Mechanism and Function of the Cytochrome bc 1 Complex -- Regulatory Mechanisms of Proton-Translocating FOF1-ATP Synthase. The present book addresses fundamental questions of biological energy transformation and conservation, with a focus on those processes which can now be understood on a structural basis. Current knowledge of selected examples of the biological energy conservation machinery such as cellular oxygen respiration, light-driven energy converters, and fermentation is reviewed. The machinery is highly variable, particularly that within microorganisms, but all of these devices universally rely on one unique underlying physico-chemical principle. The book is a rich source for specialists interested in recent developments in bioenergetics research and novices in the field alike.