The Biology Of Nitrogen Fixing Organisms

The nitrogen-fixing organisms. Free-living heterotrophic nitrogen-fixing bacteria. Nitrogen-fixing bacteria in the rhizosphere. Nitrogen fixation in the phyllosphere. Photosynthetic bacteria. Blue-gree algae. Associations with blue-green algae. Root-nodule symbioses with rhizobium. Root-nodulesymbioses withactinomycete-like organisms. Development of root-nodule symbioses. Root-nodule morphogenesis. Formation and function of bacteroids. The endophytes of the root nodules in nonleguminous plants. Leghemoglobin. Environmental effects on nodulation and symbiotic nitrogen fixation. Putative nitrogen fixation in other symbioses. The nitrogen-fixing system. The enzyme system. Genetics of N2-fixing organisms.

This book provides an introductory-level survey of biological nitrogen fixation, covering the role of the process in the global nitrogen cycle as well as its biochemistry, physiology, genetics, ecology, general biology and prospects for its future exploitation.

This 1976 volume provides information, presented at an international symposium in Edinburgh, on the free-living nitrogen-fixing bacteria and blue-green algae. In addition to information on the distribution of the nitrogenase enzyme within these groups, their role in the soil and in aquatic systems is considered, as are the methods of measuring nitrogen fixation.

Phylogenetic classification of nitrogen-fixing organisms. Physiology of nitrogen fixation in free-living heterotrophs. Nitrogen fixation by photosynthetic bacteria. Nitrogen fixation in cyanobacteria. Nitrogen fixation by methanogenic bacteria. Associative nitrogen-fixing bacteria. Actinorhizal symbioses. Ecology of bradyrhizobium and rhizobium. The rhizobium infection process. Physiology of nitrogen-fixing legume nodules: compartments, and functions. Hydrogen cycling in symbiotic bacteria. Evolution of nitrogen-fixing symbioses. The rhizobium symbiosis of the nonlegume parasponia. Genetic analysis of rhizobium nodulation. Nodulins in root nodule development. Plant genetics of symbiotic nitrogen fixation. Molecular genetics of bradyrhizobium symbioses. The enzymology of molybdenum-dependent nitrogen fixation. Alternative nitrogen fixation systems. Biochemical genetics of nitrogenase. Regulation of nitrogen fixation genes in free-living and symbiotic bacteria. Isolated iron-molybdenum cofactor of nitrogenase.

Biological nitrogen fixation has essential role in N cycle in global ecosystem. Several types of nitrogen fixing bacteria are recognized: the free-living bacteria in soil or water; symbiotic bacteria making root nodules in legumes or non-legumes; associative nitrogen fixing bacteria that resides outside the plant roots and provides fixed nitrogen to the plants; endophytic nitrogen fixing bacteria living in the roots, stems and leaves of plants. In this book there are 11 chapters related to biological nitrogen fixation, regulation of legume-rhizobium symbiosis, and agriculture and ecology of biological nitrogen fixation, including new models for autoregulation of nodulation in legumes, endophytic nitrogen fixation in sugarcane or forest trees, etc. Hopefully, this book will contribute to biological, ecological, and agricultural sciences.

This volume is a wide-ranging critical evaluation by international experts of the state of knowledge in the whole field of biological nitrogen fixation. It includes coverage of the chemistry of N2 reduction, the biochemistry and molecular biology of the molybdenum and vanadium nitrogenases. There is review of the whole range of organisms fixing N2, including the free-living and symbiotic organisms (bacteria, cyanobacteria, actinomycetes). Detailed consideration is given to the ecology and agricultural use of the root nodule bacteria, the molecular biology and biochemistry of nodule formation and fuction. The practicability of extending symbiotic N2-fixation to other systems or to greater efficiency is examined.