The Activity of Urease
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
||To observe the activity of urease and to distinguish bacteria that produce it from those
that do not
||Tubes of urea broth or agar
Slant cultures of Escherichia coli and Proteus vulgaris
- Inoculate a tube of urea broth or agar with E. coli, and another with the Proteus culture.
- Incubate the tubes at 35°C for 24 hours.
Record your observations.