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.

Understanding of biological nitrogen fixation has advanced with impressive rapidity during the last decade. As befits a developing area of Science, these advances have uncovered information and raised questions which will have, and indeed have had, repercussions in numerous other branches of science and its applications. This 'information explosion', to use one of to-day's cant idioms, was initiated by the discovery, by a group of scientists working in the Central Research laboratories of Dupont de Nemours, U. S. A. , of a reproducibly active, cell-free enzyme preparation from a nitrogen fixing bacterium. Full credit is due to them. But subsequent developments, albeit sometimes quite as impressive, have too often been marked by that familiar disorder of a developing field of research-the scramble to publish. It is a scramble which, at its best, may represent a laudable desire to inform colleagues of the latest developments; yet which too easily develops into an undignified rush for priority, wherewith to impress one's Board of Directors or Grant-giving Institution. This, in miniature, is the tragedy of scientific research to-day: desire for credit causes research to be published in little bulletins, notes and preliminary communications, so that only those intimately involved in the field really know what is happening (and even they may well not see the forest for the trees). Those outside the field, or working in peripheral areas, may glean something of what is going on from reviews and fragments presented at meetings, but the broad pattern of development is often elusive.

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.

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.

This volume discusses the most recent advances in biological nitrogen fixation, with chapters written by experts on the ecology, physiology, biochemistry and genetics of biological nitrogen fixation.

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.

Our knowledge of the biochemistry and biophysics of dinitrogen fixa tion has developed rapidly in the 15 years since the first N2-fixing enzyme system was successfully extracted from a bacterium. This peri od has produced a literature that now describes the N2 fixation reac tion and the nitrogenase enzyme itself in sophisticated terms, though a detailed reaction mechanism at the chemical level has not yet emerged. It is the purpose of the present monograph to present an in-depth re view, analysis, and integration of this research as is possible with a non-contributed publication and to relate this work to considera tions of N2 fixation that reach beyond the confines of the biochem ist's laboratory. The first section is directed as much toward the general science read er as toward the specialist. It covers the agricultural origins of man's interest in N2 fixation and also pertinent areas of taxonomy, physiology, and evolution. Ecological aspects of the subject include a comprehensive evaluation of the nitrogen cycle leading to a sub stantially greater estimate of the rate of global N2 fixation than previous ones. The treatment is of a survey fashion, in part to pro vide a general over-view of N2 fixation and in part to provide context for the biochemistry and biophysics that follow in the second section.