| Hydrogen Sulfide Production |
DESCRIPTION
Some bacteria have the enzymatic capability to degrade amino acids (cysteine, cystine etc.) that contain sulfhydryl
group (-SH) producing hydrogen sulfide. Hydrogen sulfide reacts with heavy metals such as lead or iron forming a
black precipitate. You can use TSI medium (contains iron) or prepare a nutritive agar with lead acetate (1g Pb
acetate to 100 ml nutritive agar).
Some bacteria have the enzymatic capability to degrade amino acids (cysteine, cystine etc.) that contain sulfhydryl
group (-SH) producing hydrogen sulfide. Hydrogen sulfide reacts with heavy metals such as lead or iron forming a
black precipitate. You can use TSI medium (contains iron) or prepare a nutritive agar with lead acetate (1g Pb
acetate to 100 ml nutritive agar).
MEDIUM PREPARATION
TSI composition:
Peptic peptone 10g, Casein peptone 10g, Meat extract 3g, Yeast extract
3g, Lactose 10g, Sacharose 10g, Dextrose 1g, NaCl 5g, Fe2SO4 0.2g,
Na-thyosulphate 0.3g, Phenol red 0.024g, Agar 12g, H2O ad 1000 ml.
PROCEDURE
Harvest a well isolated colony and inoculate a TSI tube by stabbing the
medium. Incubate at 37 °C, 24 hours. Reaction is positive if a black color
appears.
EXPLANATION
Bacteria growing in TSI degrade aminoacids forming ferrous sulfide which
blackens the medium.
TSI composition:
Peptic peptone 10g, Casein peptone 10g, Meat extract 3g, Yeast extract
3g, Lactose 10g, Sacharose 10g, Dextrose 1g, NaCl 5g, Fe2SO4 0.2g,
Na-thyosulphate 0.3g, Phenol red 0.024g, Agar 12g, H2O ad 1000 ml.
PROCEDURE
Harvest a well isolated colony and inoculate a TSI tube by stabbing the
medium. Incubate at 37 °C, 24 hours. Reaction is positive if a black color
appears.
EXPLANATION
Bacteria growing in TSI degrade aminoacids forming ferrous sulfide which
blackens the medium.
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.
| TSI Medium blackening due to H2S production (left tube) - Salmonella choleraesuis |
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