(Lab 3) Isolation of Nitrogen-Fixing Bacteria Flashcards
What bacteria share a mutualistic relationship with legumes?
Rhizobium
- infects root nodules and feeds on sugars
- legumes get usable form of nitrogen (NO3-)
Identify the organisms in the images. What are their features?
Azotobacter and Azomonas
- Gram-negative diploovoid
- weakly motile
- obligate aerobes
- can ferment with mannitol as sole carbon source
- facultative N2 fixers
Why are Azotobacter and Azomonas facultative N2 fixers?
It is an energy-expensive process
Why is enrichment important before isolation?
N2 fixers are a small amount of the microbiome in the soil, and creating an environment where only they can thrive makes it easier to isolate them
Why do we incubate the N2-free media with the bottle on its side with the cap slightly loose?
- obligate aerobes
- Need N2 to survive
- increase surface area of bacteria to air
Identify the bacteria shown
Azotobacter vinelandii
Identify the bacteria shown
Azotobacter chroococcum
What N2 fixer has no pigment, is gram variable, and ovoid-rod-shaped?
Azomonas macrocytogenes