Glutathione acts as an exometabolite that promotes growth recovery in fission yeast with defects in amino acid metabolism and cell polarity

Abstract

ABSTRACT 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 exometabolite-mediated interactions 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 derived from 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, 6 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 ∆ 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 identifying GSH as an exometabolite that influences cellular processes and potentially shapes microbial communities. IMPORTANCE Microorganisms 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 releases a wide variety of metabolites outside the cells, including previously reported nitrogen signaling factors (NSFs) and glutathione (GSH) identified in this work. By analyzing gene deletion mutants whose growth is supported by extracellular GSH, we provide new insights into how secreted primary exometabolites compensate for specific genetic defects and influence cell physiology in microbial populations.