Arginine dihydrolase test
From Bugwoodwiki
Purpose
Used to distinguish the Pseudomonas syringae group from other Pseudomonas spp.
Ingredients
| Ingredient | 500 mL | 1 L |
|---|---|---|
| distilled water | 500 mL | 1 L |
| peptone | 0.5 g | 1.0 g |
| NaCl | 2.5 g | 5.0 g |
| K2HPO4 | 0.15 g | 0.30 g |
| agar | 1.5 g | 3.0 g |
| phenol red | 0.005 g | 0.01 g |
| DL-Arginine HCl | 5.0 g | 10.0 g |
Instructions
- Mix the above ingredients in the appropriate amount of distilled water. Adjust the pH to a light orange-pink color (pH 7.2).
- Dispense into tubes and allow to solidify.
- Stab inoculate tubes with bacteria from a fresh culture.
- Cover tube with a few ml of sterile mineral oil. Incubate at 27°C for 4 days.
Expected results
- Development of a deep pink color indicates a positive reaction.
Notes
- Be careful not to let the pH get too high when making the medium. If the medium is too pink (high pH), it may not be possible to discern a positive reaction.
- The enzyme, arginine dihydrolase, releases ammonium from arginine. The resulting alkalinity is indicated by the pH indicator phenol red, which turns a dark pink color under oil as in contrast to the orange pink of uninoculated controls or arginine dihydrolase-negative cultures.
References
Contributed by
From the Virginia Polytechnic Institute and State University Mediabook; Orignially created by Robert Wick; contributed by Mary Ann Hansen.
