Yogurt Lab

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Yogurt Lab
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Purpose

• Use Kochs postulates to identify a
  disease-causing bacteria

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Kochs postulates

• 1. Demonstrate and record the symptoms shown.
• 2. Isolate and identify the suspected pathogen
  from the infected material and establish a pure
  culture.
• 3. Use the pure culture to infect new material.
  Describe and record symptoms shown by the
  material. Compare to original symptoms.
• 4. Isolate and identify the organism.

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How are they used?

• In the medical field, they are used to identify
  the bacteria that is making you sick.

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Day 1-

• 1. Demonstrate and record symptoms.
• Make general observations about the yogurt.
• (In this lab, the yogurt represents the diseased
  individual)
• Look at it under the microscope

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Day 1-

• Isolate and identify pathogen from infected
  material.
• Make bacteria plates with smears from milk,
  yogurt, and pure E. coli.
• The purpose is to grow the bacteria outside of
  the yogurt.
• The E. coli is to test if another bacteria can
  cause the same symptoms.

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Day 2-

• Isolate the pathogen and grow in a pure culture.
• Take the bacteria that grew on the plates and
  examine them.
• Take one colony of bacteria and re-infect the
  milk.

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Day 3

• Isolate and identify the pathogen from the newly
  diseased individual.
• Make general observations about the new cultures.
• Look at the pathogen under the microscope.

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Lab technique

• Septic technique
• When dealing with bacteria-
• Always get a clean swab.
• If theres a chance that something could be
  contaminated, throw it out.
• Keep your face away from the culture plates.
• Wear gloves
• Keep the culture plates closed as much as
  possible.

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Lab technique

• Streaking
• When growing bacteria on an agar plate, it is
  best to apply the sample in a streaking
  formation.
• Start in one quadrant and smear. Rotate 45
  degrees and smear. Rotate 2 more times.
• The last quadrant will have the least amount of
  bacteria and will be easily visible.

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