Phosphatase medium
From Bugwoodwiki
Purpose
For identifying Erwinia chrysanthemi
Ingredients
| Ingredient | 1 L |
|---|---|
| distilled water | 1 L |
| nutrient agar | 23 g |
| yeast extract | 2 g |
| agar | 20 g |
| 1% filter-sterilized phenolphthalein diphosphate tetrasodium salt | 5 mL |
| 30% ammonia hydroxide (50:50 dilution of conc. NH4OH, sp. gr. 90) | a drop |
Instructions
- Mix water, nutrient agar, yeast extract, and agar
- Autoclave
- Cool to 45-50°C
- Add 1% filter-sterilized phenolphthalein diphosphate tetrasodium salt
- Spot-inoculate plates with fresh cultures
- Incubate for 2 days at 27°C
- Place a drop of 30% ammonia hydroxide in lid of the Petri dish and invert the plate above it. Allow approximately 30 seconds for diffusion of NH3, which causes the pH to shift to the alkaline level.
Expected results
- Phosphatase-positive colonies and media become pale pink.
Notes
- It is essential that observations be completed within 1 to 1.5 minutes because a prolonged observation is less accurate due to fading color.
- Use positive and negative controls.
References
- Schaad, N. W. 1980. Laboratory Guide for the Identification of Plant Pathogenic Bacteria. The American Phytopathological Society, St. Paul, MN. 72 pp. (p. 52).
Contributed by
From the Virginia Polytechnic Institute and State University Mediabook; contributed by Mary Ann Hansen
