Description
Peptone Water is particularly suitable as a substrate in the study of indole production. Peptone used in Peptone Water is rich in tryptophan content. Presence of indole can be demonstrated using either Kovacs or Ehrlich reagent. Peptone Water is also utilized as a base for carbohydrate fermentation studies with the addition of sugar and indicators such as bromocresol purple, phenol red or bromothymol blue. Peptone Water is recommended for studying the ability of an organism to ferment a specific carbohydrate which aids in differentiation of genera and species. Peptone water is formulated as per Shread, Donovan and Lee. Peptone Water with pH adjusted to 8.4 is suitable for the cultivation and enrichment of Vibrio species. The medium consists of peptone which provides nitrogenous and carbonaceous compounds, long chain amino acids, and vitamins provides essential nutrients. Sodium chloride maintains the osmotic balance of the medium. It is also used in routine laboratory tests for detection of indole production, a red colour development after addition of reagent indicates a positive result. It is of value in differentiation work on organisms such as Escherichia coli and Yersinia spp. To ensure accuracy and repeatability of the test results, attention should be paid to the incubation and observation.
