Keynote Lecture. Nitrogen fixation in perspective; W.E. Newton. Section I: Biochemistry and Chemistry. Chemistry and biochemistry of nitrogenase; B.E. Smith. The mechanism of molybdenum nitrogenase: An overview; B.K. Burgess. Roles for nucleotides in nitrogenase catalysis; L.C. Seefeldt, et al. Superoxide-dependent nitrogen fixation; C. Hofmann-Findeklee, et al. Chemistry and biochemistry of nitrogenase (Part 1); R.N.F. Thorneley, et al. A 1.6 A resolution x-ray crystallographic study of Klebsiella pneumoniae MoFe protein, Kp1; S.M. Mayer, et al. Roles of VnfX and NifX in FeV-co and FeMo-co synthesis in Azotobacter vinelandii; C. Ruttimann-Johnson, et al. Studies on the mechanism for the activiation of iron and sulfur for formation of the nitrogenase metal centers; D.R. Dean, et al. Stopped-flow infra-red spectroscopy of carbon monoxide binding to functioning nitrogenase; R.N.F. Thorneley, et al. Reductant-dependent ATP utilization during nitrogenase catalysis: Studies using Ti (III); A.C. Nyborg, et al. Cofactor reactivity and models for cofactor reactions; G.J. Leigh, R.L. Richards. Interactions of small molecules with isolated FeMoco; C.J. Pickett, et al. Catalytic reactions with FeMoco in non-enzymatic surroundings (comparison with synthetic catalysts); A.E. Shilov. Catalytic behavior of isolated FeMo-cofactor of nitrogenase in non-protein surroundings; T.A. Bazhenova, et al. Chemical nitrogen fixation: protonation of coordinated dinitrogen with coordinated dihydrogen or bridging hydrosulfido ligands; M. Hidai. Mo, V and Fe complexes of tripodal sulfur-donor ligands as models for nitrogenase active sites; S.C. Davies, et al. The use of chemicals models to probe the mechanisms of substrate reduction reactions of nitrogenases; C.A. Helleren, et al. Poster Summaries. Section II: Regulation of Nitrogen Fixation and Assimilation. Regulation of nif gene expression in free-living diazotrophs: recent advances; M.J. Merrick, et al. Activation of transcription by the sigma-54 RNA polymerase holoenzyme; M.-T. Gallegos, et al. New mechanisms of bacterial gene regulation in a nitrogen-fixing phototroph; R.G. Kranz, et al. Regulation of nitrogen fixation and glutamine synthetase in Herbaspirillum seropedicae; E.M. Souza, et al. Analysis of bacterial gene expression during the late stages of the interaction between Rhizobium etli CNPAF512 and Phaseolus vulgaris; J. Michiels, et al. Functional analysis of the Bradyrhizobium japonicum RegSR two-component regulatory proteins; R. Emmerich, et al. Role of Herbaspirillum seropedicae NifA domains on the expression of nif genes; R.A. Monteiro, et al. Characterization of an Azospirillum brasilense Tn5 mutant with enhanced nitrogen fixation; C.A.G. Blaha, et al. amtB is necessary for NH4+ induced nitrogenase swithc-off and ADP-ribosylation in Rhodobacter capculatus; A.F. Yakunin, P.C. Hallenbeck. Regulation of Azotobacter vinelandii NifA activity by NifL: Role of PII-like proteins in nitrogen sensing; F. Reyes-Ramirez, et al. Structural basis for signal transduction within the FixJ transcriptional activator; J. Schumacher, et al. Effect of redox status of dinitrogenase reductase on the regulation of nitrogenase activity by reversible ADP-ribosylation; C.M. Halbleib, et al. Heterotrimerization of PII-like signalling proteins: Lessons from a comparative analysis between a cyanobacterial PII homologue and its proteobacterial counterparts; K. Forchhammer. Role of PII protein as a signal of nitrogen level in Herbaspirillum seropedicae; E.M. Benelli, et al. Poster Summaries. Genetics of nitrogen fixation in Rhodobacter capsulatus: Ammonium and molybdenum control of both nitrogenase systems; W. Klipp, et al. Electron transport pathway to nitrogenase in Rhodobacter capsulatus: Rnf complex and its relatives in non-diazotrophs; K. Saeki, H. Kumagai. Photosynthesis in Aeschynomene Bradyrhizobium sp. ORS278: Genetic analysis and role in symbiosis; E. Giraud, et al. The concerted action of hydrogenases and nitrogenases in cyanobacteria; H. Bothe, et al. Heterocyst pattern controlled by an inhibitory peptide in Anabaena; H.-S. Yoon, J.W. Golden. The element nitrogen in the philatelic world; H. Bothe. Section III: Taxonomy and Evolution of Diazotrophs. Taxonomy and evoluation of diazotrophs; J.P.W. Young. Ecological, phylogenetic and taxonomic remarks on diazotrophs and related genera; E. Martinez Romero, et al. Molecular evolution in diazotrophs: Do the genes agree?; J.P.W. Young. Phylogeny of Rhizobia; P. van Berkum, et al. Genetics of Nostoc in relation to host plant species; U. Rasmussen, M.M. Svenning. Origin and evolution of nif genes; R. Fani, et al. Characterization of nitrogen-fixing bacteria containing molybdenum-independent nitrogenases from diverse natural environments; D. Betancourt, et al. Biodiversity of rhizobia from a wide range of forest Leguminosae species in Brazil; F.M.S. Moreira. Biodiversity and selection of Sinorhizobium fredii strains for soybean inoculants; D.N. Rodriguez-Navarro, et al. Taxonomy of the family Acetobacteraceae; L.E. Fuentes-Ramirez, et al. Diversity in the bean nodulating rhizobial population of northwetst Argentina; O.M. Aguilar, M.V. Lopez. Poster Summaries. Section IV: Legume symbiosis. Control of nodulation in leguma symbiosis; G. Stacey. Perception of lipo-chitooligosaccharidic Nod factors in the legume-rhizobia symbiosis: Studies on Medicago nod factor-binding sites; J.-J. Bono, et al. The use of GFP to study factors involved in the Lotus japonicus symbiosis; H.P. Spaink, et al. Cell cycle control in root nodule organogenesis; A. Kondorosi, et al. Nod factor reception; G. Stacey, et al. Functional characterization of a Kruppel-like zinc finger gene induced during nodule development; F. Frugier, et al. Suppression of plant defence reactions in alfalfa cell structures by Sinorhizobium meliloti surface carbohydrates; K. Niehaus, et al. Invasion of alfalfa root nodules by the nitrogen-fixing bacterium Rhizobium meliloti; G.R.O. Campbell, et al. Structure and development of inection threads; N.J. Brewin, et al. Unusual LPS structural features and symbiotic function; R.W. Carlson, et al. Two Bradyrhizobium japonicum genes encoding putative sensor proteins; P. Muller, E. Muhlencoert. Poster Summaries. Additional Articles. Author Index.