Malonate test uses to check the ability of the organism to utilize malonate as the sole source of carbon for energy. To differentiate bacteria on the basis of a malonate utilization test. It is a colorful test to check the ability of organisms for using as the sole source of carbon as malonate. The endpoint of which is the production of alkaline metabolites that create a color change. This test is recommended as part of differentiating among the Enterobacteriaceae, especially species of Klebsiella and Salmonella.
The sodium malonate present in the medium. Malonate is an enzyme inhibitor and inhibits the utilization of succinic acid by organisms, shutting down the Krebs and glyoxylic cycles. Growth is indicative of malonate utilization as a carbon source; a small amount of glucose is also present to enhance the growth of some organisms. The presence of Inorganic ammonium salts in a medium acts as the sole source of nitrogen. When the bacterium ferments sodium malonate, sodium hydroxide and sodium bicarbonate are formed, which increases the alkalinity of the medium. The shift in pH turns the bromthymol blue indicator in the medium from green to blue. Malonate-negative organisms that ferment glucose cause the indicator to turn yellow due to acid.
Ingredients per liter of deionized or distilled water
Yeast extract 1.0 g
ammonium sulfate 2.0 g
Aipotassium phosphate 0.6 g
Monopotassium phosphate 0.4 g
Sodium chloride 2.0 g
Sodium malonate 3.0 g
Glucose 0.25 g
Bromthymol blue 0.025 g a.
Final pH, 6.7
Store at 2 to 8°C.
Sterile inoculating loops or sticks
Incubator
Control Organisms
Positive control (PC): Klebsiella pneumoniae ATCC 13883
Negative Control (NC): Escherichia coli ATCC 25922
Malonate test positive: Development of a blue color
Malonate test negative: green or turning yellow due to dextrose fermentation
Klebsiella pneumoniae ATCC 13883: malonate positive (blue color)
Escherichia coli ATCC 25922: malonate negative (green color)