Asymbiotic nitrogen-fixing bacteria and their nitrogen fixation potential

Abstract:

Biological nitrogen fixation is an important N source to ecosystems, and nitrogen-fixing microorganisms play important roles in plant growth and development. Compared with symbiotic nitrogen-fixing microorganisms, asymbiotic nitrogen-fixing microorganisms are more widely distributed and more diverse, and they are of significance to the nitrogen cycle in the global ecosystem. In this review, the classification, phylogeny and community assembly of asymbiotic nitrogen-fixing bacteria were summarized. We compared the differences of asymbiotic nitrogen-fixing bacterial compositions and their nitrogen-fixing potential in different ecosystems (such as grassland, forest, ocean, farmland, etc.) and different parts of plants (such as canopy, phyllosphere, rhizosphere, endosphere, litter, etc.). The main factors affecting the community structure and nitrogen-fixing potential of asymbiotic nitrogen-fixing bacteria include climatic factors, soil properties and artificial measures. The frequently-used methods for studying asymbiotic nitrogen-fixing bacteria and their nitrogen-fixing potential were also summarized.