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🦠microbiology review

Rhizobium leguminosarum

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Rhizobium leguminosarum is a species of nitrogen-fixing bacteria that form symbiotic relationships with leguminous plants, such as peas, beans, and alfalfa. These bacteria are able to convert atmospheric nitrogen into a form that can be readily absorbed and utilized by the host plant, making them an important component of the nitrogen cycle.

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5 Must Know Facts For Your Next Test

  1. Rhizobium leguminosarum is a member of the Proteobacteria phylum, which is known for its diverse metabolic capabilities and important roles in various ecological processes.
  2. The bacteria colonize the roots of legumes and form specialized structures called nodules, where they convert atmospheric nitrogen into ammonia that can be readily absorbed by the plant.
  3. This symbiotic relationship is beneficial for both the bacteria and the host plant, as the bacteria receive carbohydrates from the plant in exchange for the fixed nitrogen.
  4. Rhizobium leguminosarum is widely used in agriculture as a biofertilizer, as it can significantly improve the nitrogen content of the soil and reduce the need for synthetic nitrogen fertilizers.
  5. The bacteria are able to survive in the soil for extended periods, even in the absence of a host plant, and can be reintroduced to the soil through the application of inoculants.

Review Questions

  • Explain the role of Rhizobium leguminosarum in the nitrogen cycle.
    • Rhizobium leguminosarum is a key player in the nitrogen cycle, as it is able to convert atmospheric nitrogen into a form that can be readily absorbed and utilized by plants. Through a symbiotic relationship with leguminous plants, the bacteria colonize the roots and form specialized nodules, where they perform nitrogen fixation. This process converts nitrogen gas into ammonia, which the plant can then use for growth and development. The fixed nitrogen is also released into the soil, where it can be accessed by other plants, contributing to the overall fertility of the ecosystem.
  • Describe the symbiotic relationship between Rhizobium leguminosarum and leguminous plants.
    • Rhizobium leguminosarum forms a mutually beneficial symbiotic relationship with leguminous plants, such as peas, beans, and alfalfa. The bacteria colonize the roots of the host plant and form specialized structures called nodules, where they convert atmospheric nitrogen into ammonia. In exchange, the plant provides the bacteria with carbohydrates and other essential nutrients needed for their growth and survival. This symbiotic relationship is advantageous for both the bacteria and the plant, as the bacteria receive a reliable source of energy and the plant gains access to a readily available source of nitrogen, which is essential for its growth and development.
  • Evaluate the importance of Rhizobium leguminosarum in sustainable agriculture and its potential applications.
    • Rhizobium leguminosarum is considered a crucial component of sustainable agriculture due to its ability to fix atmospheric nitrogen and provide it to leguminous plants. By reducing the need for synthetic nitrogen fertilizers, the use of Rhizobium leguminosarum as a biofertilizer can help improve soil fertility, reduce environmental pollution, and promote more sustainable farming practices. Additionally, the bacteria's ability to survive in the soil for extended periods and be reintroduced through inoculants makes it a versatile and cost-effective solution for enhancing crop yields and soil health. As concerns over the environmental impact of traditional agricultural practices continue to grow, the potential applications of Rhizobium leguminosarum in sustainable agriculture are increasingly being recognized and explored.