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.

Inhalt
General Introduction.- Microorganisms Involved in the Nitrogen and Sulfur Cycles (With 2 Figures).- Nitrogen Metabolism in General.- Nitrogen Metabolism in Plants (With 5 Figures).- The Assimilatory Reduction of Nitrate.- Dissimilatory Nitrate Reduction (With 10 Figures).- Dinitrogen Fixation.- Genetics of Dinitrogen Fixation (With 1 Figure).- Rhizobium Genetics (With 7 Figures).- Some Aspects of the Physiology of Dinitrogen Fixation (With 3 Figures).- The Biochemistry of Dinitrogen Fixation (With 3 Figures).- Pathways and Regulatory Aspects of N2 and NH4+ Assimilation in N2 -Fixing Bacteria (With 1 Figure).- The Hydrogenase-Nitrogenase Relationship in Nitrogen-Fixing Organisms (With 1 Figure).- Sulfur Metabolism in General.- Assimilatory Sulfate Reduction (With 7 Figures).- Ecology and Physiology of Some Anaerobic Bacteria from the Microbial Sulfur Cycle (With 1 Figure).- Dissimilatory Sulfate Reduction, Mechanistic Aspects (With 2 Figures).- Dissimilatory Sulfate Reduction, Energetic Aspects (With 9 Figures).- Photolithotrophic Sulfur Oxidation.- Oxidation of Ammonia by Nitrosomonas and of Inorganic Sulfur by Thiobacilli (With 3 Figures).- Contributed Papers: Nitrogen Metabolism.- Enzymatic Mechanism and Regulation of Nitrate Reduction in Rhodopseudomonas capsulata.- HCN and the Control of Nitrate Reduction. The Regulation of the Amount of Active Nitrate Reductase Present in Chlorella Cells (With 4 Figures).- Regulation of Nitrate Uptake in Green Algae and Duckweeds. Effect of Starvation and Induction(With 6 Figures).- Nitrate Uptake and Reduction in Chlorella Characterisation of Nitrate Uptake in Nitrate-Grown and Nitrogen-Starved Chlorella sorokiniana (With 9 Figures).- Nitrogen Metabolism in Photosynthetically Inhibited Plants (With 5 Figures).- Investigationson the Reduction of Aliphatic and Aromatic Nitro Compounds by Clostridium Species and Enzyme Systems (With 6 Figures).- Fine Structure Analysis of the Gene Region for N2-Fixation (nif) of Klebsiella pneumoniae (With 7 Figures).- In vitro Associations Between Non-legumes and Rhizobium (With 13 Figures).- Limitations of Symbiotic and Associative Nitrogen Fixation by Developmental Stages in the Systems Rhizobium japonicum with Glycine max and Azospirillum brasilense with grasses e.g. Triticum aestivum (With 9 Figures).- Regulation of Nitrogenase Biosynthesis in Free-Living and Symbiotic N2-Fixing Bacteria: a Comparison (With 4 Figures).- Characterization of the Nitrite-Oxidizing System in Nitrobacter (With 8 Figures).- Contributed Papers: Sulfur.- The Role of Thioredoxins for Enzyme Regulation in Cyanobacteria (With 4 Figures).- Recent Results on the Assimilatory Sulfate Reduction: APS-Kinase and the reduction of APS to Cysteine in Higher Plants (With 1 Figure).- Aspects of S- and N-Metabolism in Tissue Cultures (With 4 Figures).- Regulation of Adenosine 5?-Phosphosulfate Sulfotransferase in Higher Plants (With 3 Figures).- On the Enzymatic System Thiosulfate-Cytochrome c-Oxidoreductase (With 6 Figures).