H2S test (hydrogen sulfide test) principle, procedure, reagents

H2S test is an important test in microbiology for the identification of various enterobacteria and Brucella species.

H2S test principle

H2S (hydrogen sulfide) produced by many bacteria due to reaction with sulphur containing amino-acid. This H2S (hydrogen sulfide) detected by a change in colour by the reaction of H2S and ferrous chloride leading to black colour ferrous sulphide.

H2S test (hydrogen sulfide test) Reagents

1. Ferrus chloride	10%
2. Gelatin	120 g
3. Meat extract	7.5 g
4. Sodium Chloride	5 g
5. Peptone	25 gm
Distilled Water	1 litter

H2S test (hydrogen sulfide test) procedure

1. Inoculate the colony of test organism with the help of wire loop in the depth of 1 cm to medium.
2. Incubate at 25 to 35 C.
3. Check daily for color change in the media for 7 days.
4. Black color production is the sign of H2S (Hydrogen sulphide) production.

NOTE: Medium is solidified with gelatin.

What is the positive control in H2S test

Proteus Valgaris colony use as positive control in H2S test.

What is the Negative control in H2S test

E.coli bacteria use as a negative control in the H2S test.