Nitrogen Fixation

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.

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 aims to serve as a centralized reference document for students and researchers interested in aspects of marine nitrogen fixation. Although nitrogen is a critical element in both terrestrial and aquatic productivity, and nitrogen fixation is a key process that balances losses due to denitrification in both environments, most resources on the subject focuses on the biochemistry and microbiology of such processes and the organisms involved in the terrestrial environment on symbiosis in terrestrial systems, or on largely ecological aspects in the marine environment. This book is intended to provide an overview of N2 fixation research for marine researchers, while providing a reference on marine research for researchers in other fields, including terrestrial N2 fixation. This book bridges this knowledge gap for both specialists and non-experts, and provides an in-depth overview of the important aspects of nitrogen fixation as it relates to the marine environment. This resource will be useful for researchers in the specialized field, but also useful for scientists in other disciplines who are interested in the topic. It would provide a possible text for upper division classes or graduate seminars.

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.

The turn of the millennium from the twentieth to the twenty-first century provides an occasion to review our understanding of a biological process, biological nitrogen fixation, that is of prime importance for the continued survival of mankind. This process has provided a basis for maintaining soil fertility since the beginning of organised agriculture, yet its very existence was confirmed only just over a century ago. In the intervening years, an enormous intellectual effort has dispersed much of the mystery surrounding biological nitrogen fixation. Biological fixation is widely exploited in agriculture, as are nitrogen fertilisers prepared for the last hundred years under extreme conditions of temperature and pressure. However, despite all our efforts, the fundamental nature of the reactions involved at the heart of the biological process remain unknown. This book aims to describe what we have learned in the last one hundred years or so about biological nitrogen fixation, about what its chemistry appears to be, and how it is applied in agriculture. This ambitious objective has not been attempted recently. It is aimed at students and those who wish to enter these very challenging areas of research, and who need to learn the state of the art at the turn of the millennium. The authors are all acknowledged world experts in their fields. They have prepared concise, well referenced and authoritative accounts of their subjects. This book provides a unique summary of the current state of knowledge that will be indispensable to all students and researchers, actual and potential, interested in biological nitrogen fixation.

Biological nitrogen fixation provides more than 50% of the total annual input of the essential element nitrogen to world agriculture. Thus, it is of immense agronomic importance and critical to food supplies, particularly in developing countries. This book, with chapters authored by internationally renowned experts, provides a comprehensive and detailed account of the fascinating history of the process - including the surprising discoveries of molybdenum-independent nitrogenases and superoxide-dependent nitrogenase; a review of Man's attempts to emulate the biological process - most successfully with the commercially dominant Haber-Bosch process; and the current state of the understanding art with respect to the enzymes - called nitrogenases - responsible for biological nitrogen fixation. The initial chapters use a historical approach to the biological and industrial processes, followed by an overview of assay methodologies. The next set of chapters focuses on the classical enzyme, the molybdenum nitrogenase, and details its biosynthesis, structure, composition, and mechanism of action as well as detailing both how variants of its two component proteins are constructed by recombinant DNA technology and how computational techniques are being applied. The sophisticated chemical modelling of the metal-containing clusters in the enzyme is reviewed next, followed by a description of the two molybdenum-independent nitrogenases - first, the vanadium-containing enzyme and then the iron-only nitrogenase - together with some thoughts as to why they exist! Then follows an up-to-date treatment of the clearly "non-classical" properties of the superoxide-dependent nitrogenase, which more closely resembles molybdenum-containing hydroxylases and related enzymes, like nitrate reductase, that it does the other nitrogenases. Each chapter contains an extensive list of references. This book is the self-contained first volume of a comprehensive seven-volume series. No other available work provides the up-to-date and in-depth coverage of this series and this volume. This book is intended to serve as an indispensable reference work for all scientists working in this area, including agriculture and the closely related metals-in-biology area; to assist students to enter this challenging area of research; and to provide science administrators easy access to vital relevant information.

Nitrogen fixation by leguminous plants is especially important when farmers are trying to minimise fertilizer use for cost or environmental reasons. This second edition of the highly successful book, first published in 1991, contains thoroughly updated and revised material on the theory and practice of nitrogen fixation in tropical cropping systems.

Collection, isolation and maintenance of Rhizobia and Frankia; Colletion, cultivation and maintenance of azolla; Collection, isolation, cultivation and maintenance of associative N2-fixing bacteria; Fluorescence methods for study of Rhizobium in culture and in situ; Serological techniques for Brabyrhizobium and Rhizobium identification; Enzyme-linked immunosorbent assay (ELISA) for the detection and identification of Rhizobium strains; Use of Intrinsic culture and antibiotic resistance for Rhizobium Study; Isolation and identification of genetically marked strains of nitrogen-fixing microsymbionts of soybens; Measurement of nitrogen fixation by direct means; Measurement of biological fixation using acetylene reduction; Measuring ureides; Evaluation of nitrogen fixation by legumes in the greenhouse and growth chamber; Principles and practice of field designs to evaluate symbiotic nitrogen fixation; Production and quality control of inoculants; Role of culture collectios in biological nitrogen fixation.