The Roles of Bacteria and Fungi in Plant Nutrition

Plants make their food through photosynthesis, but they also need minerals and nutrients.

Some plants rely on soil-dwelling organisms to get resources from the soil more efficiently.

Rhizobacteria are prokaryotes that live closely with plant roots. This diverse group of organisms gets nutrients from plant roots and supports the plant in several ways.

For example, they may produce antibiotics that protect the plant from harmful microbes, absorb harmful chemicals from the soil, or help plants get essential nutrients.

Nitrogen is a key component of proteins and nucleic acids. However, plants cannot use nitrogen gas directly from the atmosphere because they lack the machinery needed to convert it into usable forms.

Certain prokaryotes convert atmospheric nitrogen into ammonia through nitrogen fixation.

In soil, this ammonia quickly forms ammonium ions. Soil microbes then oxidize ammonium into nitrite and then into nitrate through nitrification. Plants absorb ammonium and nitrate and use them to grow.

In legumes, such as peas, nitrogen fixation happens in specialized root structures called nodules.

In this symbiotic relationship, Rhizobia bacteria convert atmospheric nitrogen into forms the plant can use, while the bacteria receive nutrients from the plant.

Many plants also form beneficial partnerships with fungi. These fungi, called mycorrhizal fungi, get nutrients from the plant.

In return, they help plants reach soil nutrients that would otherwise be difficult to access. For example, they help plants absorb nutrients like phosphate, copper, and zinc.

Mycorrhizal fungi can also act as a physical barrier against pathogens or produce antibiotics that help protect the plant.