Common Biochemical Tests in Microbiology: Hydrogen Sulphide Production Test

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BACKGROUND

Some of the bacteria products hydrogen sulphide (H₂S) gas mainly members of the family Enterobacteriaceae. The gas is produced when Sulphur containing amino acids like methionine, cystine is reduced. A heavy metal salt containing iron is utilized for detecting hydrogen sulfide gas production. Hydrogen gas reacts with this metal salt to form a black precipitate.¹

So, the basic objective of this test is to detect the capability of an organism to produce hydrogen sulfide gas.

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REQUIREMENTS

Sample:    Test organism

Media:     SIM media- 20 g pancreatic digest of casein + 6.1 g peptic digest of animal tissue+3.5 g Agar+0.2 g
                 Fe(NH₄)₂(SO4)₂·6H₂O + 0.2 g Na₂S₂O₃·5H₂O.

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PROCEDURE

Take a labelled tube containing SIM medium and inoculate the organism by stabbing.¹ Then incubate these tubes at 37^oC for about 24-48 hours. Then observe for the formation of black precipitation. If there is blackening of medium then, positive result and if no blackening of the medium then negative result.²

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CONCLUSION

An earliest product of bacterial decomposition that was recognized was hydrogen sulphide.

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REFERENCES

1. Hunter CA, Crecelius HG. Hydrogen sulphide studies. I. Detection of hydrogen sulphide in cultures. J. Bact. 1938; 35: 185.
   
2. Myers JT. The production of hydrogen sulphide by bacteria. J. Bact. 1920; 5: 231.