nitrogenasibakteerien

Nitrogenasibakteerien, often referred to as nitrogen-fixing bacteria, are microorganisms capable of converting atmospheric nitrogen gas (N2) into ammonia (NH3). This process, known as biological nitrogen fixation, is crucial for life on Earth as it makes atmospheric nitrogen, which is unusable by most organisms, available in a form that can be assimilated by plants and subsequently enter the food chain. These bacteria can be found in various environments, including soil, water, and symbiotic relationships with plants.

There are two main categories of nitrogen-fixing bacteria: free-living and symbiotic. Free-living bacteria, such as Azotobacter and Clostridium, exist independently in the soil or water. Symbiotic nitrogen-fixing bacteria, most notably species of Rhizobium, form specialized structures called nodules on the roots of legumes (e.g., peas, beans, clover). Within these nodules, the bacteria receive carbohydrates from the plant and, in return, supply the plant with fixed nitrogen. Other symbiotic relationships exist, such as with Frankia bacteria that fix nitrogen in non-leguminous woody plants.

The enzyme nitrogenase is central to the nitrogen fixation process. This enzyme is sensitive to oxygen and requires anaerobic or microaerobic conditions to function. The energy required for nitrogen fixation is substantial, and it is supplied by the host plant in symbiotic relationships or derived from organic matter by free-living bacteria. The ammonia produced is then readily converted into amino acids and other nitrogen-containing organic molecules. This microbial process is a vital component of the global nitrogen cycle, underpinning the productivity of terrestrial and aquatic ecosystems.