LAB 3 - Nitrogen Fixing Bacteria Flashcards
What do all living organisms require nitrogen for
To make amino acids, nucleotides, and vitamins
Nitrogen fixation
Involves reduction of molecular nitrogen (N2) to ammonia (NH3+) and incorporation into organic molecules to form amino acids
Nitrogen fixation commercial scale
Nitrogen fixing microbes are applied to soils to increase soil nitrogen content and thus increasing and maintain agricultural systems
Nitrogen fixation global scale
Essential biological process because it is major natural pathway by which nitrogen enters biosphere
Examples of nitrogen fixing bacteria
Rhizobium (only fix nitrogen when associated with leguminous plant) and Azospirillum (fix nitrogen independently) species
Nitrogen free mannitol media
Limits the types of bacteria that can grow on it, as it contains mannitol as sole carbon source and does not contain any nitrogen
Controls in isolation of nitrogen fixing bacteria experiment
- Negative control = Bacillus cereus
- Positive control = Azotobacter chroococcum
Which genera might the organisms grown in NFMB/NFMA belong to?
Azotobacter or Rhizobium
Explain the process of non-symbiotic nitrogen fixation.
- Performed by free-living bacteria like Azotobacter.
- Converts atmospheric nitrogen (N₂) to ammonia (NH₃), which can be used by plants.
Explain how the formulation of the NFMB/NFMA media helps to achieve the objectives of the experiment
- Nitrogen-free media selects for bacteria that can fix nitrogen.
- Mannitol as the sole carbon source supports the growth of specific nitrogen-fixing bacteria
What role does the mucoid phenotype play in nitrogen fixation?
Mucoid colonies often indicate protective slime layers, which help bacteria in nitrogen fixation by providing protection and maintaining microenvironment stability.
