Indole test Principle and Protocol:
Indole is a hetrocyclic aromatic compound, which is usually a product of degeneration of tryptophan.
Indole is a hetrocyclic aromatic compound, which is usually a product of degeneration of tryptophan.
Enzyme which plays a crucial role on breaking down tryptophan is called 'Tryptophanase.'
Basic reaction for breakdown of Indole:
Water + Tryptophan --[Tryptophanase]--> Indole + Pyruvate + Ammonia
Pyruvate is used for respiration or fermentation processes.
Principle:
Bacteria break down tryptophan to indole which is detected by adding Kovac's reagent which gives a cherry red color on reaction with indole.
Kovac's reagent is used to diagnose this reaction.
Kovac's reagent consists of isoamyl alcohol, para-dimethylaminobenzaldehyde and concentrated hydrochloric acid.
Indole + Kovac's reagent ---> Cherry Red Color
Indole positive organisms: Escherichia coli, Haemophilus influenzae, Streptococcus faecalis, Vibrio sp.
Indole negative organisms: Proteus mirabilis, Lactobacillus spp. , Pseudomonas sp., Salmonella sp.
