Autotrophic and methylotrophic microorganisms are able to grow at the expense of one-carbon compounds (e.g. carbon dioxide, formaldehyde) as the principal carbon sources for the synthesis of cell material, using light, inorganic compounds or one-carbon compounds as energy sources. The study of the special adaptations required in aerobic and anaerobic microorganisms to sustain an autotrophic or methylotrophic mode of life is a fascinating field of research for scientists from various disciplines. Current research efforts not only focus on fundamental aspects, i.e. metabolic pathways and their regulation, ecology, energy conversion and genetics, but also the possible application of these organisms, in waste water treatment, degradation of xenobiotics, single-cell protein production, as biocatalysts for the production of fine chemicals, draws strong attention. The aim of this series is to provide annual reviews on the biochemistry, physiology, ecology, genetics, and application of microbial autotrophs and methylotrophs. The scope of the series includes all aspects of the biology of these microbes, and will deal with phototrophic and chemolithotrophic prokaryotic autotrophs, carboxydobacteria, acetogenic-, methanogenic- and methylotrophic bacteria, as well as methylotrophic eukaryotes. The exciting advances made in recent years in the study of these organisms is reflected in the chapters of this first volume which have been written by experts in the field. We would like to express our sincere thanks to all the contributors for their stimulating and comprehensive chapters.