#rhizobium

• Bacteriorhiza — A stable symbiotic association formed between the roots of higher plants and certain soil bacteria, particularly nitrogen-fixing ones (such as Rhizobium species). Physiologically, this ecological structure allows plants (especially legumes) to assimilate atmospheric nitrogen transformed by bacteria into accessible compounds, while the microorganisms receive carbohydrates derived from photosynthesis.
• Bacteroid — A modified, enlarged, and often branched form adopted by nitrogen-fixing bacterial cells (such as Rhizobium) after entering the host cells within the nodules of legume plants. Physiologically, the bacteroid stage represents the active metabolic phase where the microorganism loses its rigid cell wall and begins synthesizing the nitrogenase enzyme complex responsible for nitrogen fixation.