Legumes have a fibrous root structure, and their roots contain little “nodules.” These nodules are home to a host of bacteria from the Genus Rhizobia. These tiny organisms complete a very important task: nitrogen fixation. Nitrogen, one of the ten elements essential for life, exists as a diatomic gas molecule under standard conditions, but is unusable for plants in its natural inorganic state. That’s where Rhizobia comes into play. The bacteria turn the root nodules of their legume hosts into nitrogen-fixing workshop, where they fix nitrogen into ammonia and other usable nitrates. The plant is then able to use the products of the nitrogen-fixation chemical reactions to form amino acids, nucleic acids, and other products necessary for life. Their nitrogen-fixation also provides considerable nutrient-return to the soil, ensuring that the soil will remain nutrient-rich enough to support plant life. As for the bacteria, their benefit is in the form of a hospitable environment in which to live and propagate, and some of the plant’s sugars as an energy source. Think about that next time you eat a bowl of black bean soup! For a more detailed analysis of this relationship, check out http://www.jic.ac.uk/science/molmicro/Rhizo.html.
So, it’s your turn: what’s an example of a cool mutualistic relationship in nature that you find interesting? Why is that relationship significant? How would it affect that community or ecosystem if one partner in the relationship were eliminated?
