| Indole Production |
DESCRIPTION
Indole is an aromatic heterocyclic organic compound that can be produced by some bacteria as a degradation
product of the amino acid tryptophan. Tryptophanase is the enzyme involved tryptophan degradation resulting
indole, pyruvate, and ammonia. Indole test is most used for coliforms identification.
Indole is an aromatic heterocyclic organic compound that can be produced by some bacteria as a degradation
product of the amino acid tryptophan. Tryptophanase is the enzyme involved tryptophan degradation resulting
indole, pyruvate, and ammonia. Indole test is most used for coliforms identification.
MATERIALS
Simplest medium for indole testing is Buffered peptone water (Proteose
peptone 10g, NaCl 5g, Disodic phosphate 3.5g, Monopotasic phosphate
1.5g,
H2O ad 1000 ml; pH 7.2), but most used for Enterobacteriaceae
identification is MIU medium (Motility Indole Urea).
PROCEDURE
Inoculate a Buffered peptone water medium or a MIU tube and incubate
at 37
°C. After 24 hours of incubation add few drops of Ehrlich-Kovacs reagent.
This will combine with the indole forming a red layer on the surface of the
medium, if the reaction is positive. Reaction is negative if no red color
appear.
Simplest medium for indole testing is Buffered peptone water (Proteose
peptone 10g, NaCl 5g, Disodic phosphate 3.5g, Monopotasic phosphate
1.5g,
H2O ad 1000 ml; pH 7.2), but most used for Enterobacteriaceae
identification is MIU medium (Motility Indole Urea).
PROCEDURE
Inoculate a Buffered peptone water medium or a MIU tube and incubate
at 37
°C. After 24 hours of incubation add few drops of Ehrlich-Kovacs reagent.
This will combine with the indole forming a red layer on the surface of the
medium, if the reaction is positive. Reaction is negative if no red color
appear.
REFERENCES
1. H. Raducanescu, V.Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
2. Margaret Barnett, 1992. Microbiology Laboratory Exercises. Wm. C. Brown Publishers.
1. H. Raducanescu, V.Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
2. Margaret Barnett, 1992. Microbiology Laboratory Exercises. Wm. C. Brown Publishers.
| Indole positive result - red ring on MIU medium surface (middle tube) |
NOTES
Indole should not be tested after 4-5 days of incubation because bacteria may further degrade indole and a false
negative result may occur.
Indole should not be tested after 4-5 days of incubation because bacteria may further degrade indole and a false
negative result may occur.
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