The Activity of Urease


Diagnostic Microbiology In Action
  Principles of Diagnostic Microbiology
    Primary Media for Isolation of Microorganisms
    Some Metabolic Activities of Bacteria
      Simple Carbohydrate Fermentations
      Starch Hydrolysis
      Production of Indole and Hydrogen Sulfide, and Motility
    Activities of Bacterial Enzymes
      The Activity of Urease
      The Activity of Catalase
      The Activity of Gelatinase
      The Activity of Deoxyribonuclease (Dnase)
      The Activity of a Deaminase
    Principles of Antigen Detection and Nucleic Acid Assays for Detection Identification of Microorganisms
      Antigen Detection Assays
      Enzyme Immunoassay (Eia)
      Nucleic Acid Detection Assays

Some bacteria split the urea molecule in two, releasing carbon dioxide and ammonia. This reaction, mediated by the enzyme urease, can be seen in culture medium in which urea has been added as the substrate. Phenol red is also added as a pH indicator. When bacterial cells that produce urease are grown in this medium, urea is degraded, ammonia is released, and the pH becomes alkaline. This pH shift is detected by a change in the indicator color from orange-pink to dark pink (see colorplate 20).
Rapid urease production is characteristic of Proteus species and of a few other enteric bacteria that at one time were classified in the Proteus genus. This simple test can be useful, therefore, in distinguishing these organisms from other bacteria that resemble them.

Purpose To observe the activity of urease and to distinguish bacteria that produce it from those
that do not
Materials Tubes of urea broth or agar
Slant cultures of Escherichia coli and Proteus vulgaris

  1. Inoculate a tube of urea broth or agar with E. coli, and another with the Proteus culture.
  2. Incubate the tubes at 35°C for 24 hours.

Record your observations.