Identification of Yeast Strain Genetic Factors in the Formation of Volatile Sulfur

To date we have confirmed the high degree of variation in H2S formation among commercial yeast strains and natural isolates. In general, all display an increase in H2S formation upon nitrogen and pantothenate limitation, but the magnitude of the effect varies widely among the strains. Some are far more sensitive to limiting nutrients than are others. The degree of response is not well-correlated with the intrinsic sulfite reduction activity as determined from color on BiGGY agar suggesting that factors other than the activity of this pathway are critical in hydrogen sulfide production. Glutathione addition to the medium did not appear to impact H2S formation. Internal glutathione levels were manipulated using two metabolic inhibitors, which seemed to have an effect on lag phase but not total amount of H2S formed once cells had adapted to the inhibitor. This adaptation would be prevented in the presence of both inhibitors, which is currently being investigated. This work has provided an important foundation for comparison of the protein and gene expression profiles of strains grown under conditions of low and high hydrogen sulfide formation.