Production of Hydrogen Sulphide

The raw material hydrogen sulphide (H2S) is commonly used in the synthesis of a variety of sulphur-containing chemicals.

The interaction of hydrogen and sulphur produces high-purity ((≧99.9 %) H2S in the hydrogen sulphide synthesis process. The production plant is small and compact, making it simple and safe to produce highly dangerous hydrogen sulphide.

During metabolism, some bacteria can degrade sulphur (Sulphur) containing substances to hydrogen sulphide, which is often used as a test measure in laboratories to identify them. To detect the production of hydrogen sulphide (H2S) by microorganisms, various approaches are utilised, which differ depending on the sulphur source and the metal salts used to indicate H2S  synthesis. Because of its semi-solid form, lack of interfering carbohydrates, and use of peptonised iron as an indicator, SIM is more sensitive than TSI or KIA in detecting H2S. On the other hand, lead acetate paper is ten times as sensitive as other media.

Principle

The test medium contains an iron compound and a sulphur component to see if hydrogen sulphide production happens. If the sulphur component is reduced by the bacterial strain, hydrogen sulphide is generated. As a result, this test determines whether the bacterium converts sulphur-containing molecules to sulphides as part of its metabolism. 

During protein degradation or when anaerobic respiration shuttles electrons to sulphur instead of oxygen, certain bacteria make H2S by minimising the negative impact of amino acids like cysteine and methionine or reducing inorganic sulphur compounds like thiosulfates, sulphates, or sulfites. H2S (hydrogen sulphide gas) is created in either case, which combines with the iron component to form the black ferric sulphide precipitate. The presence of hydrogen sulphide is indicated by the black colour. The detection of hydrogen sulphide (H2S) gas produced by a living organism is primarily utilised to aid in the identification of that organism.

Let us discuss the production of hydrogen sulphide examples.

Production of H2S from Sodium Thiosulphate

Many bacteria destroy sodium thiosulphate by the production of hydrogen sulphide (H2S). Parallel to the cysteine micro tests, micro tests for H2S generation from sodium thiosulphate using 1 per cent Na2S2O3 at pH 68 per cent were done. The reaction was slower than cysteine, with blackening appearing after 2–4 hours. Some of the negative isolates were retested at pH 75.5 or 79.5 and showed mild blackening after 4 to 24 hours. Most strains tested positive in the routine test; however, the reaction was frequently milder than with cysteine.

Sal. Lexington, Sal. gallinarum, Sal. typhisuis, Sal. paratyphi A, Sal. Potsdam, Sal. pullorum, and one strain each of Sal. typhi, and Sal. Paratyphi B were all found to be negative Salmonella species. When retested at pH 75, the two last ones were positive. Retesting at pH 75 revealed that 7 among them were weakly positive. At pH 6·8, none of the Proteus strains created H2S from thiosulphate, and none of the Pr. rettgeri strains produced H2S from thiosulphate at pH 7·5. Negative thiosulphate results could simply indicate that the test’s sensitivity limit has been reached, not that the organism is incapable of destroying thiosulphate.

Production of H2S from Sodium Sulphite

Sodium sulphite was also tested at 1% concentration at pH 6·8, or 7·5; few organisms generated more than traces of blackening in these experiments. Therefore it was not included in the standard series. The reaction was slower than with cysteine or thiosulphate, and blackening was rarely seen before 4 hours, and most positive strains did not show blackening until 24 hours. The results were unaffected by adding glucose to the organism’s growth media or the substrate.

Uses

• It is mostly used to identify members of the Enterobacteriaceae family and, on rare occasions, to distinguish other bacteria. 

•  The test facilitates the identification of different bacteria. 

• It’s particularly useful for recognising Salmonella, Francisella, and Proteus bacteria.

Limitations

• For species that use sucrose, TSI may limit H2S formation by suppressing the enzyme mechanism that causes H2S generation.

• Bacteria are poisonous to lead acetate, and it may prevent the growth of some bacteria. Allow no media to come into contact with the strip.

Conclusion

Natural sources account for the majority of the production of hydrogen sulphide in the air. It is made when bacteria decompose plant and animal matter in stagnant waters with low oxygen levels, including bogs and swamps. Hydrogen sulphide is also released by volcanoes, hot springs, and underwater thermal vents.