Glutathione acts as an exometabolite that rescues functionally distinct genetic mutations in fission yeast

Microorganisms in nature form communities through diverse interactions, such as mutualism and competition, to adapt to their ecological environments. These interactions seem to be mediated by extracellular metabolites (exometabolites), yet the chemical and biological diversity underlying these processes remains largely unexplored. In this study, we examined the chemical basis of cell-cell communication in the fission yeast Schizosaccharomyces pombe by a genome-wide screen employing 3,420 viable gene deletion mutants. We identified 37 strains that exhibited growth defects in monoculture on a minimal medium but exhibited growth recovery in the vicinity of wild-type colonies (co-culture), suggesting that exometabolites secreted by wild-type cells compensated for the gene deletion. Both lipophilic and water-soluble fractions obtained by solvent partitioning of the wild-type culture supernatant promoted growth recovery. Among the 11 mutants rescued by the water-soluble fraction, six were cysteine auxotrophs, prompting analyses of thiol-containing metabolites by liquid chromatography-mass spectrometry (LC-MS), revealing the presence of glutathione (GSH) in the culture supernatant. GSH restored growth in most strains as a nutrient source. In contrast, GSH rescued cell morphology defects in the hob3{Delta} mutant, lacking the Bin/Amphiphysin/Rvs (BAR) adaptor protein Hob3, through a mechanism independent of nutrition. This research advances understanding of exometabolite-mediated interactions in S. pombe by highlighting the role of GSH as one of the communication molecules that influence cellular processes and shape microbial communities. Author summaryMicroorganisms secrete a wide range of metabolites that control microbial community behavior. These extracellular metabolites (exometabolites) include not only well-studied signaling molecules but also diverse primary and secondary metabolites, suggesting complex interactions among microbes. However, the molecular basis of these interactions remains poorly understood, partly due to challenges in detecting them experimentally. In this study, we surveyed exometabolites involved in cell-cell interactions in the model eukaryotic microorganism Schizosaccharomyces pombe. S. pombe secretes a wide variety of metabolites, including previously reported nitrogen signaling factors (NSFs) and glutathione identified in this work. By analyzing gene deletion mutants that depend on GSH for growth, we provide new insights into how microbes regulate collective behavior by sharing exometabolites.