Collective production of hydrogen sulfide gas enables budding yeast lacking < i > MET17 < /i > to overcome their metabolic defect

by Sonal, Alex E. Yuan, Xueqin Yang, Wenying Shou

Assimilation of sulfur is vital to all organisms. InS.cerevisiae, inorganic sulfate is first reduced to sulfide, which is then affixed to an organic carbon backbone by the Met17 enzyme. The resulting homocysteine can then be converted to all other essential organosulfurs such as methionine, cysteine, and glutathione. This pathway has been known for nearly half a century, andmet17 mutants have long been classified as organosulfur auxotrophs, which are unable to grow on sulfate as their sole sulfur source. Surprisingly, we found thatmet17Δ could grow on sulfate, albeit only at sufficiently high cell densities. We show that the accumulation of hydrogen sulfide gas underpins this density-dependent growth ofmet17Δ on sulfate and that the locusYLL058W (HSU1) enablesmet17Δ cells to assimilate hydrogen sulfide. Hsu1 protein is induced during sulfur starvation and under exposure to high sulfide concentrations in wild-type cells, and the gene has a pleiotropic role in sulfur assimilation. In a mathematical model, the low efficiency of sulfide assimilation inmet17Δ can explain the observed density-dependent growth ofmet17Δ on sulfate. Thus, having uncovered and explained the paradoxical growth of a commonly used “auxotroph,” our findings may impact the design of future studies in yeast genetics, metabolism, and volatile-mediated microbial interactions.

Source: PLoS Biology: Archived Table of Contents - December 7, 2023 Category: Biology Authors: Sonal Source Type: research