Three CBGP groups participate in comprehensive two-volume set Biological Nitrogen Fixation.
Nitrogen gas (N2) is the most abundant molecule in the atmosphere, but it can only be directly used as nutrient by a relatively small number of bacteria that can synthesize the metalloenzyme nitrogenase. These diazotrophic bacteria can convert (fix) N2 into ammonia that will be used to synthesize amino acids and nucleic acids. As a result, the soils where they live are “fertilized” with combined nitrogen species that can be used by plants to grow. No other organisms can carry out this process, and the equivalent industrial process requires of large amounts of energy to create the conditions (300-500ºC, 250 atm of N2 and H2) to fix N2. Interest in biological nitrogen fixation is rising, as an alternative to the overuse of chemical nitrogen fertilizers that have severe environmental and economical costs.
Three CBGP groups have participated in the elaboration of a two-volume set of books entitled Biological Nitrogen Fixation, directed to emphasize the molecular techniques and advanced biochemical analysis approaches applicable to biological nitrogen fixation. Members of the group “Genomics and Biotechnology of Plant-Associated Diazotrophic Bacteria” describe in their chapter a pipeline to use genomic data from pooled DNA samples (pool-seq) to study the selection of specific rhizobial genotypes of Rhizobium leguminosarum bv viciae by different host plants. Rhizobia are a subset of diazotrophic bacteria that only fix N2 when living as endosymbionts in legume nodule cells. These nodules are developed by the host plant as result of a complex exchange of chemical signals, transduction pathways that are critical for the symbiosis to be established. Members from the group “Metal Homeostasis in Plant-Microbe Interactions”, in collaboration with the groups of Dr. M. Udvardi and Dr. V. Benedito describe the strategies to select and functionally analyse transcription factors mediating nodule development, as well as transporters responsible for nutrient exchange between the two symbionts. Biological N2 fixation is an energetically expensive process, and consequently, it is tightly regulated to avoid the loss of valuable resources. This is reviewed by members of the group “Biochemistry of Nitrogen Fixation” using the free-living diazotroph Azotobacter vinelandii as model. Finally, in another chapter, this same group reviews current knowledge on the biosynthesis of the unique iron-molybdenum cofactor found at the nitrogenase active site.