Nitrogen and sulfur compounds are continuously synthetized, degraded and converted into other forms in nature. There are many similarities in the principle problems and basic mechanisms of the biology of inorganic nitrogen and sulfur. Many details are not yet understood and hence are the subject of active investigation the world over. In May, 1980, a conference was held in Bochum, Federal Republic of Germany, at which attempts were made to discuss and compare all aspects of both the nitrogen and the sulfur cycle. Lectures were given by internationally recognized experts on the physiology, biochemistry, genetics, and ecology of dinitrogen fIXation, of assimilatory and dissimilatory nitrate and sulfate reduction, and of ammonia and sulfide oxidation. In addition, important data were communicated by German scientists of the national program on the Metabolism of Inorganic Nitrogen and Sulfur Compounds, supported by the Deutsche Forschungsgemeinschaft. This book contains all the contributions to the meeting and consequently should be of interest to researchers, teachers, and students in the field. The members of the German national program on the Metabolism of Inorganic Nitrogen and Sulfur Compounds would like to thank the Deutsche F orschungsgemeinschaft for their generous fmancial support of the scientific projects during the past four years and for the conference itself. Without this help, the present book would not have been written. The members express their appreciation particularly to Dr. A. Hoffmann of the Deutsche Forschungsgemeinschaft for her invaluable skill and patience in taking care of the projects and scientists.