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Hemoglobin in five genetically diverse Frankia strains.
Jason Beckwith1, John D Tjepkema, Robert E Cashon
1Department of Biological Sciences, University of Maine, 5722 Deering Hall, Orono, ME 04469-5722, USA.
Canadian Journal of Microbiology
|March 7, 2003
Summary
Hemoglobin is common in Frankia, a nitrogen-fixing bacteria, and its production is not directly linked to nitrogen fixation. This hemoglobin likely aids in oxygen transport, facilitating bacterial growth under varying conditions.
Area of Science:
- Microbiology
- Biochemistry
- Plant Science
Background:
- Frankia bacteria are crucial for nitrogen fixation in symbiotic relationships with plants.
- The presence and function of hemoglobin in Frankia are not fully understood.
- Hemoglobin is known to bind oxygen, potentially playing a role in oxygen transport.
Purpose of the Study:
- To investigate the prevalence of hemoglobin in diverse Frankia strains.
- To determine the relationship between hemoglobin production and nitrogen fixation.
- To characterize the properties and potential function of Frankia hemoglobin.
Main Methods:
- Culturing five genetically diverse Frankia strains under varying nitrogen and oxygen conditions.
- Measuring hemoglobin concentration and biomass production.
- Analyzing hemoglobin molecular mass and oxygen dissociation rates using size exclusion chromatography and spectrophotometry.
Main Results:
- All five Frankia strains produced hemoglobin irrespective of nitrogen availability (-N or +N).
- Hemoglobin concentration in Frankia strain EAN1(pec) was higher at 2% O2 than 20% O2 under -N conditions.
- Frankia produced significantly more biomass with combined nitrogen (+N) and with 0.2% CO2, and the hemoglobin exhibited rapid oxygen dissociation rates.
Conclusions:
- Hemoglobin is a common protein in Frankia and its production is independent of nitrogen fixation.
- Frankia hemoglobin is likely a truncated type, functioning in facilitated oxygen diffusion to support bacterial growth.
- Optimized oxygen and carbon dioxide levels enhance Frankia biomass production.