One of the pleasures with working in the area of nitrogen fixation is the fact that while the actual reduction of nitrogen gas (dinitrogen) to ammonia would appear to be a well defined process, many research questions remain and continue to be addressed by diverse groups of scientists including chemists, biochemists, physiologists, molecular biologists, evolutionary biologists, ecologists and applied agricultural scientists. Every two years or so, these groups meet to discuss their most recent findings.

About 300 registrants from 44 countries world-wide attended the thirteenth International Congress on Nitrogen Fixation, which took place in Hamilton, Ontario, Canada on July 2-7, 2001. During the Congress, some 70 oral and approximately 200 poster presentations were made. This volume represents written documentation of these presentations. The very broad participation and wide range of topics justifies our book title, Nitrogen Fixation: Global Prospectives.

The Congress included reports on the continuing progress in understanding the catalytic mechanism of dinitrogen reduction by the conventional molybdenum-containing nitrogenase including the latest ideas on where substrates bind on the biologically unique prosthetic group called FeMo-co. In addition, we heard that homologs of NifHDK which are the structural components of nitrogenase, catalyze steps in chlorophyll synthesis in Rhodobacter capsulatus. Further characterization of the Streptomyces thermoautotrophicus nitrogenase underlined just how little this enzyme has in common with the conventional nitrogenase.

Genomics was well represented at the Congress. The complete nucleotide sequence and annotation of the Mesorhizobium loti and Sinorhizobium meliloti genomes were described along with further sequence analyzes of the symbiotic regions from Bradyrhizobium japonicum and M. loti. It is expected that these genomes will lead to the identification of additional symbiotic genes. Clearly the large numbers of genes with unknown function open up the possibility of much future research.

In the area of plant genomics, we saw that work on the construction of refined maps of the Lotus japonicus and Medicago truncatula genomes is well underway. One report outlined exciting progress on the identification of a receptor kinase gene which may be the site of a non-nodulating mutation in alfalfa.

The integration and impact of phylogeny on microbiology continues in the area of nitrogen fixation. Of particular note was the identification of rhizobia-like bacteria that induce nitrogen-fixing root nodules on leguminous plants in the p division of the Proteobacteria. That report strengthens the view that the diversity of the rhizobacteria remains to be fully realized.

Overall, from the lively discussions we witnessed in both the auditoria and the hallways, we judged this Congress to be a satisfying and worthwhile experience for the participants. We hope this volume will be a reminder of those good times and a ready reference source of the invaluable information shared in Hamilton. Not all was bright, however, and with sadness and respect, we acknowledge the passing of several of our colleagues from the nitrogen-fixation community.

Finally, we wish to take this opportunity to thank all of the individuals, who helped organize this Congress and to thank the organizations, listed elsewhere, without whose support this Congress would not have been possible. We thank Marlene Mirza for her tireless work in helping to organize the Congress and Vicki Newton for her work and guidance towards getting this book published. We thank Hanna Lindemann, Barbara Reuter, Allyson MacLean, Barbara Finan and Elizabeth Weretilnyk, and most importantly, we thank McMaster University for financial, secretarial, and administrative support throughout the organization of the Congress.

Turlough Finan David Layzell Mark O'Brian Kevin Vessey William Newton

Hamilton, August 15th, 2001

Johanna Döbereiner Memorial Lecture

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