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Life in grasses: diazotrophic endophytes
1Max-Planck-Institute for Terrestrial Microbiology, Marburg, Germany. reinhold@mailer.uni-marburg.de
Trends in Microbiology
|May 20, 1998
Summary
Nitrogen-fixing bacteria like Azoarcus spp. infect plants without symptoms but don't survive in soil. These bacteria spread systemically within plant tissues, remaining physiologically active in the apoplast.
Area of Science:
- Plant-microbe interactions
- Bacteriology
- Plant physiology
Background:
- Nitrogen (N2)-fixing bacteria, including Azoarcus spp., Herbaspirillum spp., and Acetobacter diazotrophicus, are known to associate with plants.
- These bacteria can enter plant tissues but their survival and activity within the host remain areas of investigation.
Purpose of the Study:
- To investigate the infection dynamics and physiological activity of N2-fixing bacteria within gramineous plants.
- To determine if these bacteria establish endosymbiotic relationships or merely colonize plant tissues.
Main Methods:
- Infection assays with gramineous plants using selected N2-fixing bacterial species.
- Microscopic examination of plant tissues to assess bacterial localization and spread.
- Physiological assays to determine bacterial activity within the plant apoplast.
Main Results:
- N2-fixing bacteria successfully infected gramineous plants, penetrating central tissues and spreading systemically.
- No evidence of endosymbiosis within living plant cells was found.
- Bacteria were observed to be physiologically active within the plant apoplast.
- These bacteria do not survive in the soil environment.
Conclusions:
- N2-fixing bacteria can colonize gramineous plants internally without causing disease symptoms.
- The bacteria exhibit systemic spread and physiological activity within the plant apoplast, but do not form endosymbiotic relationships.
- The soil environment is not a suitable habitat for these plant-associated N2-fixing bacteria.