19 On MacConkey agar Enterobacter are lactose-fermenting, producing shiny pink colonies.
20 Vogues Proskauer Testused to detect acetoin in a bacterial broth culture- The test is performed by adding alpha-naphthol and potassium hydroxide to the Voges-Proskauer broth which has been inoculated with bacteria. A cherry red color indicates a positive result, while a yellow-brown color indicates a negative result
21 Vogues Proskauer Test- digestion of glucose to acetylmethylcarbinol. If glucose is being broken down, it will react with alpha-naphthol (VP reagent 1) and potassium hydroxide (VP reagent 2) to form a red color. Alpha-naphthol and potassium hydroxide are chemicals that detect acetoin.
22 Citrate Utilization Test - The test is based on the ability of an organism to use citrate as its only source of carbon.Bacteria that can grow on this medium turn the Bromothymolblue indicator from green to blue.
23 Indole ProductionWhen C.tetani is cultured in a medium which contains tryptophan. Indole production is detected by Kovac’s reagent which contains 4 (p)-dimethylaminobenzaldehyde which reacts with the indole to produce a red coloured compound.
24 Urease TestThe test organism is cultured in a medium which contains urea and the indicator phenol red.When the strain is urease producing, the enzyme will break down the urea (by hydrolysis) to give ammonia and carbon dioxide. With the release of ammonia, the medium becomes alkaline as shown by a changein colour of the indicator to pink-red.