Kings medium B

Purpose

For distinguishing fluorescent pseudomonads from nonfluorescent pseudomonads

Ingredients

Ingredient	1 L	500 ml
Distilled water	1 L	500 ml
proteose peptone #3 (Difco)	20 g	10 g
K2HPO4	1.5 g	0.75 g
MgSO4•7H2O	1.5 g	0.75 g
glycerol	10 mL	5 ml
agar	15 g	7.5 g

Instructions

1. Mix water and peptone first
2. Bring it to a boil and dissolve
3. Add other chemicals
4. Heat until all dissolve.

Notes

• This medium is the best general isolation medium for bacteria. Fluorescent pseudomonads produce a yellow pigment that fluoresces under longwave ultraviolet light (366 nm). Some isolates from the P. syringae group don’t fluoresce.

• This medium may not be suitable for longer term (more than 2 days) storage of Erwinia because some may die on it within a few days to a week.

• It is important to use proteose peptone #3 and not other peptones in order to allow colonies to produce fluorescent pigments.

• This mix is also commercially available as Difco Pseudomonas agar F.

References

• Schaad, N. W. 1980. Laboratory Guide for the Identification of Plant Pathogenic Bacteria. The American Phytopathological Society, St. Paul, MN. 72 pp. (p. 3)

Contributed by

From the Virginia Tech Mediabook; Orignially created by Robert Wick; contributed by Mary Ann Hansen

Images

Photo by Donald Groth, Louisiana State University AgCenter, Bugwood.org

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