Biological nitrogen fixation

Research carried out by Vincent Greffe

Leguminous plants play a crucial role in natural ecosystems as well as in agriculture. They contribute one third of the dietary protein nitrogen needs of the world’s population and account for over 27% of primary crop production. Perhaps the most distinguishing feature of legumes is their natural ability to acquire nitrogen from the air through symbiotic interaction with a group of soil bacteria collectively called rhizobia. Nitrogen is the critical limiting element for growth of most plants and is a building block of all life, being part of nucleic acids, amino acids and proteins. Consequently, the nitrogen-fixing symbiosis confers a clear advantage under nitrogen-limiting conditions and a better understanding of the process is expected to benefit worldwide food supply as well as the environment. 

Rhizobia can trigger host plants to form root nodules, specialized organs that offer the bacteria an exclusive ecological niche in which they reduce atmospheric dinitrogen to ammonia. Ammonia is made available to the plant, which in turn provides carbon sources to the bacteria.

Research within our group is aimed at achieving a better understanding of the bean - Rhizobium etli symbiosis in order to improve the efficiency of biological nitrogen fixation. To this end, we focus on several aspects of the symbiotic process. A main area of research comprises molecular and genetic mechanisms that contribute to bacterial stress resistance. Rhizobia encounter stress during free-living growth in the soil, but also during infection of the host as well as within the particular microenvironment provided by the specialized root nodules. We believe that improving bacterial stress resistance is key to increasing symbiotic performance.

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