Overview
The effect of the bacteria on amino acids that contain sulfur, frequently leads to the release of hydrogen sulfide, which is shown by using heavy metal salts such as iron. The hydrogen sulfide reacts with these metals turning the culture medium a dark color.

To detect the capacity of producing hydrogen sulfide, the Kliger medium is also used, the medium contains sodium thiosulfate, which is a substrate that is needed for the production of hydrogen sulfide, iron citrate and ammonium as a source of Fe+3 ions, which are combined with the hydrogen sulfide and they produce iron sulfide that is observed as a black precipitate on the culture medium.

Carrying out the practical
The KIA medium is inoculated using an inoculation needle that is inserted in the center of the surface of the slant culture towards the bottom of the test tube, it is taken out and the slanted surface is streaked.

Incubate for 24 hours at 37ºC. After incubation the black cultured precipitate might or might not appear.

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