Comparing symbiotic efficiency between swollen versus nonswollen rhizobial bacteroids.
1Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108, USA. oonox001@umn.edu
Plant Physiology
|September 15, 2010
Summary
Swollen bacteroids in legume nodules provide greater plant benefits, enhancing nitrogen fixation and growth. This terminal differentiation, observed in some legumes, appears to evolve for increased host fitness.
Area of Science:
- Plant-microbe interactions
- Nitrogen fixation symbiosis
- Legume biology
Background:
- Rhizobia bacteria form nitrogen-fixing nodules in legumes.
- Bacteroid differentiation in nodules can be terminal or reversible depending on the legume species.
- Plant-induced bacteroid modification impacts symbiotic efficiency.
Purpose of the Study:
- To compare the symbiotic efficiency of rhizobia in hosts inducing swollen, non-reproductive bacteroids versus hosts inducing nonswollen, reproductive bacteroids.
- To investigate the host fitness benefits associated with different bacteroid differentiation states.
Main Methods:
- Tested dual-host rhizobia strains (Rhizobium leguminosarum A34 and Bradyrhizobium sp. 32H1) in different legume hosts (peas, beans, peanuts, cowpeas).
- Assessed symbiotic efficiency using two measures: return on nodule construction cost and nitrogen fixation efficiency.
- Quantified plant growth per gram nodule growth and nitrogenase activity relative to CO2 respiration.
Main Results:
- Swollen bacteroids conferred greater net host benefit in both comparisons.
- Hosts with swollen bacteroids showed a higher return on nodule construction cost.
- Nitrogen fixation efficiency was also higher in hosts with swollen bacteroids.
Conclusions:
- Terminal bacteroid differentiation into swollen forms enhances host fitness.
- Independent evolution of terminal differentiation suggests significant fitness advantages for the plant.
- Bacteroid morphology is a key factor in optimizing legume-nodule symbiosis effectiveness.
Related Concept Videos
01:26Microbial Interactions: Cooperation
Microbial cooperation involves beneficial interactions in which different species work together for individual or mutual advantage. These interactions can profoundly influence ecological dynamics and evolutionary processes, and they are essential to many pathogenic and symbiotic relationships.Nematode–Bacteria CooperationA striking example is the relationship between the Gram-negative bacterium Xenorhabdus nematophila and the parasitic nematode Steinernema carpocapsae. Juvenile nematodes...
01:09Microbe-Plant Interactions
Microbe-plant interactions represent a dynamic spectrum of associations shaped by intricate chemical signaling. These interactions can be neutral, beneficial, or detrimental, and profoundly influence plant physiology, growth, and ecosystem function. The plant microbiome, comprising bacteria, fungi, archaea, protists, and viruses, plays a pivotal role in mediating these effects through surface colonization, internal colonization, or systemic symbiosis.Mutualistic associations, particularly with...