Rhizobia and other nitrogen fixers: Prokaryotic nitrogen fixation. A Model System for the Analysis of a Biological Process, edited by E.W. Triplett

Abstract

Horizon Scientific Press, 2000. £119.99/US$239.99 hbk (xix + 800 pages)ISBN 1 898486 19 0Since its discovery in 1886, several aspects of the process of biological nitrogen fixation have attracted the interest of researchers. For instance, the study of the nitrogenase enzyme complex has become an excellent model system for the characterization of a multi-component enzyme whose activity is restricted to anaerobic conditions. The study of specific associations between higher plants and nitrogen-fixing prokaryotes, such as the intracellular symbioses between rhizobia and legumes that lead to the formation of special plant organs, as well as associations between grasses and diazotrophic endophytes, has led to progress in the understanding of plant developmental biology in general, and in the signal exchange in plant–microorganism interactions in particular. Furthermore, these associations provide an opportunity to study the co- evolution of micro- and macrosymbionts by comparing their phylogenies.In Prokaryotic Nitrogen Fixation. A Model System for the Analysis of a Biological Process, an attempt has been made to present a state-of-the-art summary of the different aspects of research in the area of biological nitrogen fixation. The organization of the book is straightforward. In the first chapters, the nitrogen cycle is explained and oceanic nitrogen fixation is discussed based on the filamentous non-heterocystous cyanobacterium Trichodesmium. In the following six chapters, diverse studies on structure and function of the nitrogenase enzyme are summarized, ranging from site-directed mutagenesis of bacterial genes encoding components of the nitrogenase complex, to structural analysis of nitrogenase protein components by crystallography to infra-red spectroscopy of functioning nitrogenase. In the next section, some examples from free-living nitrogen-fixing bacteria are used to illustrate the possibilities for the regulation of nitrogen fixation, and aspects of the evolution of symbiotic nitrogen fixation are discussed in three excellent chapters on the evolution of root nodule symbioses and one on termite symbionts. The 20 following chapters are devoted to symbiotic nitrogen fixation in legume root nodules, without a doubt the most well researched symbiotic nitrogen-fixing system. Rhizobial chemotaxis and competition, the signal exchange between both symbionts and the infection process in general, as well as the role of rhizobial surface structures in symbiosis are discussed. Eight chapters cover plant gene expression in the course of nodule organogenesis and nodule metabolism. Progress made in genomics of diazotrophic bacteria is discussed based on three rhizobial and one archaeal example. One of the rhizobial examples covers the famous ‘symbiosis island’ in Mesorhizobium, which is transposable and can render a non-symbiotic strain of Mesorhizobium fully symbiotic1xEvolution of rhizobia by acquisition of a 500-kb symbiosis island that integrates into a phe-tRNA gene. Sullivan, J.T. and Ronson, C.W. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 5145–5149Crossref | PubMed | Scopus (303)See all