Kelman's TZC Agar (4)

TZC Stock Solution: Dissolve 1 g of 2,3,5-triphenyl tetrazolium chloride (TZC) in 100 ml of distilled water.  Place in a light-proof capped bottle, and autoclave for only 8 min or sterilize by filtration.  Store refrigerated.

Basal Medium: 


10 g (or 2.5 g)*


10 g

Casamino acids

1 g


18 g

Distilled water

1000 ml

* Modification by reducing to 2.5 g results in a better growth rate, especially of the potato strain.  Sucrose can be used as a substitute.

Preparation for plating:  The basal medium can be autoclaved and stored, then melted as needed.  To each liter of cooled, melted basal medium, add 5 ml of the TZC stock solution to give a final concentration of 0.005% (aliquots of 200 ml are recommended for ease of handling; to these, 1 ml of TZC stock solution is added).

Plating and storing:  Pour approximately 20 ml per petri plate.  When the agar is set, store inverted.  Keep 1-2 days before using to permit surface drying.  Long term storage may result in poor bacterial growth.

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