What process involves microorganisms converting atmospheric nitrogen into a usable form for plants?

The process of nitrogen fixation involves microorganisms, such as certain bacteria and cyanobacteria, converting atmospheric nitrogen (N₂) into ammonia (NH₃) or related compounds that are usable by plants. This is crucial because most plants cannot directly use atmospheric nitrogen, which makes up about 78% of the Earth's atmosphere. Instead, they rely on nitrogen fixation to convert nitrogen into a form (like nitrates or ammonium) that can be absorbed through their roots and utilized for growth and development, particularly for synthesizing essential proteins and nucleic acids.

This process is vital for the nitrogen cycle in ecosystems, as it replenishes soil nitrogen levels, allowing for healthy plant growth, and ultimately supports the entire food chain. The role of specific bacteria, such as Rhizobium, which form symbiotic relationships with leguminous plants, highlights the importance of nitrogen fixation in agriculture and natural ecosystems alike.

While photosynthesis refers to the process by which plants convert sunlight into chemical energy, fermentation is a metabolic process that extracts energy from carbohydrates under anaerobic conditions, and nitrogen assimilation describes how plants absorb and incorporate nitrogen into organic compounds after it has been made available, none of these processes directly involve the conversion of atmospheric nitrogen into a usable form for plants.