An association between bacteria and root nodules of legume is called

The association between bacteria and root nodules of legumes is called mutualism. Mutualism is a type of symbiotic relationship in which both organisms involved benefit from the interaction. In this case, the bacteria (such as Rhizobia) take nitrogen from the air and convert it into a form that can be used by the plant, while the plant provides the bacteria with a source of energy in the form of carbohydrates. This allows the plant to grow better in nitrogen-poor soils and the bacteria to obtain nutrients from the plant. This type of mutualistic relationship is important in agriculture, as legumes are often used as a crop to naturally enrich soil with nitrogen.