A Sensitive Visual Method for the Detection of Hydrogen Sulfide-Producing Bacteria

Begin with a plate containing a suspension of various hydrogen sulfide-producing bacteria capable of metabolizing sulfur-rich compounds.

Add a bismuth chloride solution that contains L-cysteine as a sulfur source and briefly incubate the mixture.

During incubation, the bacteria utilize L-cysteine and produce hydrogen sulfide, which reacts with bismuth ions to form an insoluble black bismuth sulfide precipitate.

This reaction changes the solution's color from light yellow to black, indicating hydrogen sulfide production.

Next, perform the assay using varying concentrations of sodium hydrosulfide as a hydrogen sulfide standard and add bismuth chloride.

This generates a color gradient ranging from light to intense black, representing the hydrogen sulfide levels.

Now, use this gradient to visually compare and estimate hydrogen sulfide levels in the bacterial samples, enabling the rapid detection of hydrogen sulfide-producing bacteria.

Mix 100 microliters of bacterial culture with 100 microliters of newly prepared bismuth solution in the 96-well microtiter plates, and culture for 20 minutes at 37 degrees Celsius. For each bacterial strain, perform the analysis in triplicate.

After 20 minutes, check for color change. If the color of the solution changes from light yellow to black, this indicates that the bacteria is able to produce hydrogen sulfide or H2S. Repeat this measurement three times.

Determine the sensitivity of the method using different concentrations of sodium hydrosulfide mixed with bismuth sulfide solution. Finally, determine the presence of bisulfide and sulfide ions by observing the formation of a black bismuth sulfide precipitate. Score the color of the wells using a visual scale from no color production to the darkest black color production.