The present volume contains 17 lectures of the 41 st Mosbach Colloquium of the Gesellschaft fiir Biologische Chemie, held from April 5-7, 1990 on the topic "The Molecular Basis of Bacterial Metabolism". From the beginning it was not the intention of the organizers to present a comprehensive account, but rather to select new, exciting progress on sometimes exotic reactions of specifically bacterial, mainly anaerobic metabolism. Members of our society had contributed to this progress to an extent that greatly stimulated the scientific exchange with international colleagues during the days in Mosbach. The editors hope that this stimulation will be conveyed to the readers of the articles, which reach from the biochemistry of methanogenesis, via anaerobic radical reactions, metal biochemistry in hydrogen and nitrogen metabolism, conversions of light - and redox energy, to the regulation of metabolic adaptation, and the attempts to bioengineer novel pathways for the degradation of xenobiotica. We believe that the book represents a highly progressive field of over lapping disciplines, comprising microbiology and molecular genetics, chemistry of biomimetic interest, and biophysics, and that it gives insight into the impact modern technologies have on microbiological research today. The colloquium was generously supported by the Deutsche Forschungsgemeinschaft, the Paul-Martini-Stiftung, and the Fonds fiir Biologische Chemie. A. Trebst, G. Schafer, and D. Oesterhelt were a great help in preparing the program and we wish to thank them for their advice.