This study investigates hydrogen sulfide (H2S) production from thiosulfate by Escherichia coli, using both non-proliferating cell suspensions and cell-free extracts. Artman found that H2S production required pyruvate or acetaldehyde as hydrogen donors; other organic acids and alcohols had no enhancing effect or were inhibitory. Glucose enhanced H2S production by generating pyruvate through glycolysis. Notably, H2S was not produced from sulfite, bisulfite, or sulfate under any conditions tested. Cell-free extract experiments revealed that H2S production required inorganic phosphate, magnesium ions, cocarboxylase, and coenzyme A—factors associated with the pyruvic dehydrogenase system. Surprisingly, DPN (nicotinamide adenine dinucleotide) was not essential, unlike in typical pyruvate oxidation. The author proposes that thiosulfate functions as a primary hydrogen acceptor alternative to thioctic acid, with its disulfide bond enabling this role. The specificity of pyruvate as a hydrogen donor and the independence from DPN suggest a distinct reductive mechanism linked to thiosulfate's unique chemical structure.

Key findings

• H2S production from thiosulfate by E. coli requires pyruvate or acetaldehyde as specific hydrogen donors; other organic acids and most other compounds do not enhance or actively inhibit the reaction
• Cell-free extract studies demonstrate that H2S production requires magnesium ions, inorganic phosphate, cocarboxylase, and coenzyme A, but notably not DPN
• H2S cannot be produced from sulfite, bisulfite, or sulfate regardless of substrate conditions
• Thiosulfate likely functions as a primary hydrogen acceptor with its disulfide bond serving as an alternative to thioctic acid in pyruvate oxidation