Hugh-Liefson medium
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Contents |
Purpose
For identifying the genus Erwinia.
Ingredients
Main solution
| Ingredient | 100 ml | 300 ml | 1000 ml |
|---|---|---|---|
| Peptone | 0.2 g | 0.6 g | 2 g g |
| NaCl | 0.5 g | 1.5 g | 5 g |
| KH2PO4 | 0.03 g | 0.09 g | 0.3 g |
| agar | 0.3 g | 0.9 g | 3 g |
| bromothymol blue (1% aqueous) | 0.3 ml | 0.9 ml | 3 ml |
Glucose solution
| Ingredient | 100 ml | 300 ml | 1000 ml |
|---|---|---|---|
| Glucose | 1 g | 3 g | 10 g |
| dH2O | 6 ml | 18 ml | 60 ml |
Instructions
- Adjust pH to 7.1
- Autoclave both solutions separately.
- Pour together after autoclaving.
- Aseptically disperse into sterile tubes.
- Fill each tube about 2/3 full.
- Stab inoculate two tubes per isolate.
- Pour 1-2 ml of sterile mineral oil on top of the medium in one tube.
- A positive reaction (anaerobic growth) is indicated by a yellow color in both tubes in 24 hours at 27°C. A green color indicates a negative reaction even if growth is visible.
Notes
- Hugh/Leifson Medium is used for determining the ability of an isolate to utilize glucose anaerobically (fermentation).
- This medium is the HL medium prepared from scratch.
Expected results
- A positive reaction is characteristic of Erwinia as well as other members in the Enterobacteraceae, but Erwinia is the only bacterial plant pathogen that gives a positive reaction. Strict aerobes, such as Pseudomonas and Xanthomonas, will only grow in the upper portion of the tube lacking mineral oil.
References
- Fahy, P. C., and Persley, G. J. 1983. Plant Bacterial Diseases, A Diagnostic Guide. Academic Press, New York. 393 pp.
- Hugh, R. and E. Leifson. 1953. The taxonomic significance of fermentative versus oxidative metabolism of carbohydrates by various Gram-negative bacteria. J. Bact. 66: 24-26.
Contributed by
From the Virginia Tech Mediabook; Orignially created by Robert L. Wick; contributed by Mary Ann Hansen
