The Biology Of 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.

Nitrogen is arguably the most important nutrient required by plants. However, the availability of nitrogen is limited in many soils and although the earth's atmosphere consists of 78.1% nitrogen gas (N2) plants are unable to use this form of nitrogen. To compensate , modern agriculture has been highly reliant on industrial nitrogen fertilizers to achieve maximum crop productivity. However, a great deal of fossil fuel is required for the production and delivery of nitrogen fertilizer. Moreover carbon dioxide (CO2) which is released during fossil fuel combustion contributes to the greenhouse effect and run off of nitrate leads to eutrophication of the waterways. Biological nitrogen fixation is an alternative to nitrogen fertilizer. It is carried out by prokaryotes using an enzyme complex called nitrogenase and results in atmospheric N2 being reduced into a form of nitrogen diazotrophic organisms and plants are able to use (ammonia). It is this process and its major players which will be discussed in this book. Biological Nitrogen Fixation is a comprehensive two volume work bringing together both review and original research articles on key topics in nitrogen fixation. Chapters across both volumes emphasize molecular techniques and advanced biochemical analysis approaches applicable to various aspects of biological nitrogen fixation. Volume 1 explores the chemistry and biochemistry of nitrogenases, nif gene regulation, the taxonomy, evolution, and genomics of nitrogen fixing organisms, as well as their physiology and metabolism. Volume 2 covers the symbiotic interaction of nitrogen fixing organisms with their host plants, including nodulation and symbiotic nitrogen fixation, plant and microbial "omics", cyanobacteria, diazotrophs and non-legumes, field studies and inoculum preparation, as well as nitrogen fixation and cereals. Covering the full breadth of current nitrogen fixation research and expanding it towards future advances in the field, Biological Nitrogen Fixation will be a one-stop reference for microbial ecologists and environmental microbiologists as well as plant and agricultural researchers working on crop sustainability.

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.

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.

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.

The process of converting atmospheric nitrogen into ammonia and other nitrogenous compounds in soil is termed as nitrogen fixation. Most of the biological nitrogen is fixed by prokaryotic bacteria. A few of these are cyanobacteria, azotobacter, azospirillum, rhizobium and bradyrhizobium. Clover, soybean, peanut, etc., are some of the plants which help in nitrogen fixation process. These processes are part of the nitrogen cycle. They are of utmost significance in agriculture as nitrogen is required for the synthesis of various organic compounds like amino acids, nucleic acids and proteins. Nitrogen is also fixed by natural phenomenon such as lightning. It is also responsible for the formation of nitrogen oxides which may react with water to form nitrous acid or nitric acid. The acids seep into the soil where they are converted into nitrates. This book includes some of the vital pieces of work being conducted across the world, on various topics related to nitrogen fixation. From theories to research to practical applications, case studies related to all contemporary topics of relevance to this field have been included in it. This book is a vital tool for all researching or studying the biological and ecological aspects of nitrogen fixation as it gives incredible insights into emerging trends and concepts.

The core of the text is aimed at the research worker in the field of nitrogen fixation, but, despite its specialisation, does not lose the emphasis on teaching, both as a direct reference book and as a backbone for a graduate course on the subject.The closing part of the book includes a subject index and a glossary of terms. The latter was included not for the expert, for whom many of the definitions will be too general, but for the newcomer; the author hopes that the quick survey of key terms will help in the reading of this book.