How do Rhizobium bacteria help legume plants grow?

Rhizobium bacteria support the growth of legumes through a mutualistic symbiosis that enables nitrogen fixation.12

While atmospheric nitrogen is abundant, it is not directly usable by plants. Rhizobium bacteria invade the root hairs of host plants, stimulating the formation of root nodules—specialized structures where the bacteria reside. Within these nodules, the bacteria convert atmospheric nitrogen into ammonia, a form of nitrogen that the host plant can readily utilize for its development and protein synthesis.12

In exchange for this essential nutrient, the legume plant provides the bacteria with a home and the necessary subsistence for their survival. This biological process is vital for soil health, as it naturally enriches the environment with nitrogen compounds that can benefit other plants once the host legume decays.2