Acid and/or Gas production from Carbohydrates
From Bugwoodwiki
Purpose
The ability to produce acid from carbohydrates is an important feature for the identification of bacteria. The bromcresol purple is a pH indicator that will turn yellow in the presence of acid.
Ingredients
| Ingredient | 1 L | 500 ml | 250 ml |
|---|---|---|---|
| Distilled water | 1000 ml | 500 ml | 250 ml |
| Peptone | 10 g | 5 g | 2.5 g |
| Bromcresol purple (1.5% ETOH solution) | 0.7 ml | 0.35 ml | 0.175 ml |
Instructions
- Dissolve peptone and bromcresol purple in distilled water.
- Dispense 4.5 ml into 8 ml disposable test tubes. Cap and autoclave, allow to cool. Carbohydrates are dissolved to make 10% working solutions, then filter-sterilized directly into each test tube of autoclaved peptone solution. Swirl to mix.
- The final concentration of carbohydrate is 1.0%. Some carbohydrates such as palatinose are expensive and excess solution should not be made up (allow enough beyond the 0.5 ml/tube to moisten the disposable filters). Also, testing with expensive carbohydrates should be done only for isolates where the additional information would be diagnostic.
- To inoculate tubes of different carbohydrates, the loop need only be charged with the culture once. A series of tubes can then be inoculated more efficiently. The small amount of carbohydrate carry-over will not affect the results.
- Incubate at 27 °C for 7 days. Some publications call for incubation for as long as 14 days. For meaningful comparisons of results, the tests should be carried out in the same way that was reported for the data to be compared with.
- For bacteria that will not grow in the absence of growth factors, Medium C of Dye must be used. This medium contains yeast extract and a 0.5% final concentration of carbohydrate.
Notes
- The ability to produce acid from carbohydrates is an important feature for the identification of bacteria. The Bromcresol purple is a pH indicator and will turn yellow in the presence of acid.
- Gas from glucose is determined by submerging a Durham tube (without trapping air) into the peptone broth, prior to autoclaving (autoclaving usually drives the air out of the submerged test tubes). Glucose is then added by filter sterilization after autoclaving.
References
- Fahy, P. C., and G. J. Persley. 1983. Plant Bacterial Diseases, A Diagnostic Guide. Academic Press, New York. 393 pp.
- Dye, D. W. 1968. A taxonomic study of the genus Erwinia. I. The "Amylovora" Group. New Zealand Journal of Science. 11: 590-607
Contributed by
From the Culture Media for Plant Pathogenic Fungi and Bacteria, University of Massachusetts: Contributed by Robert L. Wick
