Nitrogen deficiency is often found to be a limiting factor to plant growth and has significant ecological and agricultural implications. This may seem like a paradox based on the fact that the atmosphere around us is comprised by 80% nitrogen (N2).
However, in its pure form atmospheric nitrogen is a chemically stable gas and only organisms belonging to the group of prokaryotes are capable of reducing N2 to a form which can be assimilated biologically.
The gram-negative soil bacterium Sinorhizobium meliloti is able to interact with the roots of both alfalfa (Medicago sativa) and the model legume Medicago truncatula to form nodules in which atmospheric nitrogen can be converted to ammonia. From the initial contact between the bacterium and its host plant to the development of functional nodules this plant/microbe interaction is a fascinating biological phenomenon involving many finely regulated processes in both bacteria and host plants.
Our research in this field mainly concentrates on the study of genes and molecules enabling S. meliloti to invade and colonize roots of its host plants.
Presently we are working on the following aspects of S. meliloti / plant interactions:
- Characterization of the exact biochemical function of the two genes thuA and thuB from Sinorhizobium meliloti known to be involved in nodulation competitiveness on certain host genotypes.
- Understanding the timing of excretion of plant root- and microbial exudates during plant-microbe interaction.
We study these problems using classical biochemical- as well as modern molecular biology methods.