The focus of Dr. Ribbe’s research is the assembly and mechanism of nitrogenase, one of the most complex metalloenzymes known to date. Nitrogenase can be appreciated from the perspective of the useful agricultural and industrial products it generates, namely, ammonia, hydrogen and hydrocarbons. During his Ph.D. work, Dr. Ribbe focused on a fourth type of nitrogenase from a thermophilic bacterium, Streptomyces thermoautotrophicus. This nitrogenase differs from the three previously-discovered nitrogenases in subunit composition and structural properties; more importantly, it couples CO oxidation to N2 reduction, thereby connecting two biotechnologically applicable processes together. Since the beginning of his independent career, Dr. Ribbe has focused his efforts on investigating the biosynthesis of the “conventional” Mo-nitrogenase from Azotobacter vinelandii and, in particular, the unique metal centers of its MoFe protein component: FeMoco and P-cluster. Results of these studies have firmly established nitrogenase MoFe protein as a model system that could be used to deduce the general mechanism of metal cluster assembly and develop successful strategies for synthesizing bio-inspired catalysts for industrial usage. Recently, Dr. Ribbe expanded his research to the investigation of the structure and function of the “alternative” V-nitrogenase from Azotobacter vinelandii. His discovery that V-nitrogenase can convert CO to hydrocarbons provides a potential blueprint for developing cost-efficient processes for industrial production of biofuels in the future.