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34: Urea Hydrolysis

Objectives

  • Understand the reactions of bacteria in urea broth

UREA

Urea can be broken down with the help of the enzyme urease, producing the alkaline product of ammonia plus carbon dioxide. That causes the pH indicator phenol red to turn a beautiful shade of hot pink.

MATERIALS NEEDED

  • 1 urea broth for unknown bacterium

THE PROCEDURE

  1. Inoculate the tube of urea broth with your unknown bacterium.
  2. Incubate until next period at optimal temperature, 30º C or 37º C.

INTERPRETATION

 

 

  1. The alkaline reaction turns the pH indicator to hot pink.
  2. A yellowish color is still a negative reaction, although acidic.
  3. Some bacteria will produce a WEAK reaction, with a bit of pink in the tube.  This should be recorded as weak +. 
  4. It is a good idea to compare your tube with an uninoculated to make sure that you do not have a weak + result.

 

 

 

 

 

QUESTIONS

  1. Is the end product being tested for an acidic, basic, OR neutral chemical? Name it.
  2. Name the indicator in this medium.

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