A look inside the root nodule

Symbiosis between a soybean and nodule bacteria

Like many legumes, soybeans (Glycine max) form a symbiosis with nitrogen-fixing bacteria of the genus Rhizobium. As part of this partnership, special structures, known as root nodules, form on the roots of the plant.

Based on a light microscope thin section of a soybean root, this model provides a view into the nodule inside. There, the Rhizobium bacteria convert the atmospheric nitrogen into ammonia, a usable source of nitrogen for the plant. In return, the plant supplies the bacteria with sugar. The root cells infected by the bacteria are coloured red.

This symbiosis not only promotes the growth of the bean, but also improves soil fertility by making the nitrogen cycle more efficient and reducing the use of external nitrogen fertiliser. In this way, the partnership makes a sustainable contribution to the health of our ecosystem.

The detail view hanging in the window shows a section of individual infected plant cells. The Rhizobium bacteria are tightly packed in the cell. They are located in demarcated spaces, so-called symbiosomes, which are formed when the bacteria are taken up into the cell. The illustration is based on an electron microscope image of a root nodule.

Materials used: Tracing paper, gauze, willow branches, papier-mâché, pigments, graphite

Alexandra Hendrikoff | Munich | 2024