Potato Malt Agar

Composition**

Final pH (at 25°C) 7.4±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 10.5 grams in 100 ml distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Mix well before pouring into sterile Petri plates.

Principle And Interpretation

Smuts are fungi that cause plant diseases affecting cereal crops. Potato Malt Agar, formulated as described by Fischer, is used for cultivating and maintaining smut fungi and other phytopathogenic fungi. In addition to smut fungi, this medium can also be used for cultivation of other organisms causing plant disease and aciduric microorganisms, which needs high carbohydrate content and neutral to slight alkaline pH for the optimal growth (1).

Malt extract which contains dextrin, maltose, a little glucose, along with the potato infusion in the medium promotes luxuriant growth of fungi (2). Peptic digest of animal tissue provides the nitrogenous compounds and trace minerals to the organisms. Sucrose supports the growth of microorganisms such as yeasts.

Quality Control

Appearance
Cream to yellow homogeneous free flowing powder

Gelling
Firm, comparable with 2.0% Agar gel.

Colour and Clarity of prepared medium
Yellow coloured clear to slightly opalescent gel forms in Petri plates

Reaction
Reaction of 10.5% w/v aqueous solution at 25°C. pH: 7.4±0.2

pH
7.20-7.60

Cultural Response

M404: Cultural characteristics observed after an incubation at 25-30°C for 40-48 hours.

Note: *: Formerly known as Aspergillus niger

Storage and Shelf Life

Store below 30°C in tightly closed container and the prepared medium at 2 - 8°C. Use before expiry date on the label.

Reference

1. Atlas R. M., 2004, Handbook of Microbiological Media, Lawrence C. Parks (Ed.), 3rd Edition, CRC Press.
2. Vanderzant C. and Splittstoesser D. F., (Eds), 1992, Compendium of Methods for the Microbiological Examination of Foods, 3rd Ed., APHA, Washington D.C.