Tryptone Water, TW

Tryptone Water is a particular liquid medium designed to qualitatively identify the formation of indole by microorganisms mainly those related to the Enterobacteriaceae family, particularly Escherichia coli.
Peptone, the main component of the medium, is source of nitrogen and, more importantly, a source of tryptophan, the amino acid substrate required for the synthesis of indole. An inducible enzyme called tryptophanase is produced following an organismal inoculation. Tryptophan is hydrolyzed by this enzyme, producing ammonia, pyruvic acid, and indole as byproducts. One way to see the build-up of indole in the medium is to add Kovacs’ or Ehrlich’s reagent, which reacts with the indole to create a distinctive red color.
It is important to note that indole synthesis is not a confirmation test for E. coli, even if it is a presumptive test. To confirm the organism’s identity, additional biochemical and/or immunological characterization is necessary for positive indole results.
Tryptone Water is mostly employed in the bacteriological analysis of water, food, and clinical samples for screening purposes, in combination with other selective and differential media.

Storage
Keep the container at 15-30 °C and prepared medium at 2-8 °C.