ABSTRACT
Recent progress in molecular biology enables an understanding of the phylogenetic relations among soil bacteria, molecular mechanisms of environmental responses, plant-microbe interactions, and bacterial genomics. If this knowledge is integrated with knowledge of traditional ecology of soil bacteria, a new interdisciplinary area, “genetic ecology of soil microbes,” could be established, which would be challenging and, perhaps, provide perspectives for fundamental questions in soil microbiology, such as diversity, endemism, adaptation, and interactions with other organisms. There are two different approaches to study the genetic ecology of soil microbes: (1) community analyses at the level of genera, species, and functions using genetic tools in the soil ecosystem, and (2) genetic autecology of a specific genus and species that is prevalent in soils. In this chapter, soybean bradyrhizobia are one of the targets for the latter approach in terms of their autochthonous features as soil bacteria, symbiotic interactions with plants, ecology, physiology, and genetics. Soybean bradyrhizobia not only have two lifestyles, free-living and symbiotic, but also polyphasic biochemical traits that may affect other soil microbes and plants. Moreover, diversity and endemism have been studied as the result of practical applications in soybean production.The aim of this chapter is to present an overview of the phylogeny, ecology, genetics, symbiotic associations, and biochemical features of soybean bradyrhizobia, and to raise perspectives for the microbial autecology of soybean bradyrhizobia. Because of constraints of space and time, it is not possible to cite all papers 349
relevant to the subject, and only papers that serve as examples for certain topics are cited.
