(Lab 3) Isolation of Nitrogen-Fixing Bacteria Flashcards

1
Q

What bacteria share a mutualistic relationship with legumes?

A

Rhizobium
- infects root nodules and feeds on sugars
- legumes get usable form of nitrogen (NO3-)

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2
Q

Identify the organisms in the images. What are their features?

A

Azotobacter and Azomonas
- Gram-negative diploovoid
- weakly motile
- obligate aerobes
- can ferment with mannitol as sole carbon source
- facultative N2 fixers

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3
Q

Why are Azotobacter and Azomonas facultative N2 fixers?

A

It is an energy-expensive process

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4
Q

Why is enrichment important before isolation?

A

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

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5
Q

Why do we incubate the N2-free media with the bottle on its side with the cap slightly loose?

A
  • obligate aerobes
  • Need N2 to survive
  • increase surface area of bacteria to air
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6
Q

Identify the bacteria shown

A

Azotobacter vinelandii

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7
Q

Identify the bacteria shown

A

Azotobacter chroococcum

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8
Q

What N2 fixer has no pigment, is gram variable, and ovoid-rod-shaped?

A

Azomonas macrocytogenes

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