INDOLE TEST
Aim To test whether the given bacterial culture can produce indole from tryptophan. Principle The indole test demonstrates the ability of certain bacteria to decompose the amino acid tryptophan to indole. Tryptophanase is an enzyme produced by certain bacteria to degrade the tryptophan in the peptone and other components of media to indole, pyruvate, indole acetic acid and ammonia. Indole combines p-dimethylaminobenzaldehyde in Kovac’s reagent and the solution turns from yellow to cherry red colour. Kovac’s reagent also contains amyl alcohol which is not water soluble, the red coloration will form in an oily layer at the top of the broth. Materials required · 24-48 hour old bacterial culture · Kovac’s reagent · Tubes containing 1% Tryptone broth(5 ml in each tub...

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