In SIM media, how is indole production detected after Kovac's reagent is added?

In SIM media, how is indole production detected after Kovac's reagent is added?

• A. A red ring forms in the Kovac's reagent layer.
• B. No color change indicates indole production.
• C. A blue ring forms in the Kovac's reagent layer.
• D. Gas production indicates indole production.

Answer: (B)

Indole production in SIM is detected by a color change produced when Kovac’s reagent is added. If the organism has tryptophanase and makes indole from tryptophan, the indole reacts with the components in Kovac’s reagent to form a red dye that concentrates at the interface, giving a red ring on the reagent layer. If indole isn’t produced, no red ring appears and the layer remains colorless or pale. Blue color or gas production are not indicators for indole in this test.

Indole production in SIM is detected by a color change produced when Kovac’s reagent is added. If the organism has tryptophanase and makes indole from tryptophan, the indole reacts with the components in Kovac’s reagent to form a red dye that concentrates at the interface, giving a red ring on the reagent layer. If indole isn’t produced, no red ring appears and the layer remains colorless or pale. Blue color or gas production are not indicators for indole in this test.