This volume covers all aspects of fundamental and applied nitrogen-fixation research, extending from biochemistry and chemistry through genetics, regulation and physiology to agricultural practice and environmental impact. It describes recent progress on studies of potential catalysts for nitrogen fixation; how the N2-fixing process is regulated in living cells; the use and impact of genetics and genomics on our understanding of the biological process; the wide variety of associations of nitrogen-fixing microbes with plants, including the formalized Rhizobium-legume and actinorrhizal associations as well as the less formalized associative and endophytic interactions; and the impact of nitrogen fixation in agriculture and forestry, including its effect on the environment. This volume provides an up-to-date referenced source, which can be readily accessed by all practicing and otherwise interested proponents of nitrogen fixation research, including those with related interests in the areas of plant and microbial science, genomics, plant-microbe interactions, genetics and regulation, plant growth and biocontrol, agriculture, forestry, ecology, taxonomy and evolution.