Arginine dihydrolase medium
From Bugwoodwiki
Purpose
Used to distinguish the Pseudomonas syringae group from other Pseudomonas spp.
Ingredients
| Ingredient | 500 ml | 250 ml |
|---|---|---|
| Distilled water | 500 ml | 250 ml |
| Bacto peptone | 0.5 g | 0.25 g |
| NaC1 | 2.5 g | 1.25 g |
| K2HPO4 | 0.15 g | 0.075 g |
| Phenol red | 0.005 g | 0.0025 g |
| L-Arginine HCL * | 5 g | 2.5 g |
| Agar | 1.5 g | 0.75 g |
Instructions
- Heat to melt the agar and dispense 4 ml per 100 mm disposable tube. Autoclave. The medium should be orange-pink.
- Stab-inoculate tubes in duplicate then seal one tube with about 1 cm depth of sterile mineral oil. Incubate for 3-7 days at 27 °C depending on original work. 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 opposed to the orange-pink of uninoculated controls. The unsealed inoculated tube will turn pink but is only to serve as a "positive control."
- Use 1% of the L form or 2% of the DL form.
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
- Fahy, P. C., and Persley, G. J. 1983. Plant Bacterial Diseases, A Diagnostic Guide. (p.356). Academic Press, New York. 393 pp.
- Thornley, M. J. 1960. The differentiation of Pseudomonas from other Gram-negative bacteria on the basis of arginine metabolism. Journal of Applied Bacteriology 23:37-52.
Contributed by
From the Culture Media for Plant Pathogenic Fungi and Bacteria, University of Massachusetts: Contributed by Robert L. Wick
