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Rhizobium meliloti exopolysaccharides: synthesis and symbiotic function
J E González1, G M York, G C Walker
1Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
Gene
|November 7, 1996
Summary
Bacterial exopolysaccharide (EPS) is crucial for nitrogen-fixing symbiosis. Low-molecular-weight (LMW) EPS acts as a signaling molecule, enabling bacterial invasion of host plant root nodules.
Area of Science:
- Microbiology
- Plant Science
- Biochemistry
Background:
- Bacterial exopolysaccharide (EPS) is essential for the nitrogen-fixing symbiosis between Rhizobium meliloti and Medicago sativa (alfalfa).
- The exact function of EPS in this symbiosis remains unclear.
- EPS-deficient bacterial mutants form nodules but fail to invade them.
Purpose of the Study:
- To elucidate the specific role of bacterial exopolysaccharide (EPS) in the Rhizobium meliloti-Medicago sativa symbiosis.
- To investigate the function of low-molecular-weight (LMW) EPS in bacterial root nodule invasion.
Main Methods:
- Utilizing bacterial mutants deficient in exopolysaccharide (EPS) production.
- Analyzing nodule formation and bacterial invasion in Medicago sativa roots.
- Investigating the effects of low-molecular-weight (LMW) EPS on bacterial invasion.
Main Results:
- Bacterial mutants lacking EPS can initiate nodule development on Medicago sativa roots.
- These EPS-deficient mutants are unable to successfully invade the induced root nodules.
- Small amounts of low-molecular-weight (LMW) EPS can restore invasion capability in EPS-deficient mutants.
Conclusions:
- Exopolysaccharide (EPS) plays a critical role in the invasion step of the Rhizobium meliloti-Medicago sativa symbiosis.
- Low-molecular-weight (LMW) EPS appears to function as a signaling molecule mediating bacterial entry into host root nodules.