Agronomy Degree Practice Exam

Bacteria from which genera associate with legumes to utilize atmospheric nitrogen?

1. Bacillus

2. Rhizobium

3. Nitrosomonas

4. Aspergillus

The correct answer is: Rhizobium

The correct answer highlights the specific relationship that certain bacteria have with legumes to enhance their nitrogen utilization. Rhizobium is a genus of bacteria known for its symbiotic association with leguminous plants. In this relationship, the bacteria colonize the root nodules of legumes and convert atmospheric nitrogen (N2) into ammonia (NH3) through the process of nitrogen fixation. This conversion is vital for the plant, as it can then incorporate this nitrogen into essential compounds such as amino acids and nucleotides, which are crucial for growth and development. This symbiotic partnership is beneficial for both organisms: the legume provides carbohydrates and a suitable environment for the bacteria, while the bacteria provide a vital nutrient source for the legume. This relationship is integral in sustainable agricultural practices, as it improves soil fertility and reduces the need for synthetic nitrogen fertilizers. The other genera mentioned are not associated with legumes for nitrogen fixation. Bacillus, for instance, encompasses a wide range of bacteria with various roles, but it does not form the same symbiotic relationship. Nitrosomonas is involved in the nitrification process, converting ammonia into nitrites, not directly with nitrogen fixation in legumes. Aspergillus, a genus of fungi, is primarily known for its roles in