Project description:Candida glabrata is a human-associated opportunistic fungal pathogen. It shares its niche with Lactobacillus spp. in the gastrointestinal and vaginal tract. In fact, Lactobacillus species are thought to competitively prevent Candida overgrowth. We investigated the molecular aspects of this antifungal effect by analyzing the interaction of C. glabrata strains with Limosilactobacillus fermentum. From a collection of clinical C. glabrata isolates, we identified strains with different sensitivities to L. fermentum in coculture. We analyzed the variation of their expression pattern to isolate the specific response to L. fermentum. C. glabrata-L. fermentum coculture induced genes associated with ergosterol biosynthesis, weak acid stress, and drug/chemical stress. L. fermentum coculture depleted C. glabrata ergosterol. The reduction of ergosterol was dependent on the Lactobacillus species, even in coculture with different Candida species. We found a similar ergosterol-depleting effect with other lactobacillus strains (Lactobacillus crispatus and Lactobacillus rhamosus) on Candida albicans, Candida tropicalis, and Candida krusei. The addition of ergosterol improved C. glabrata growth in the coculture. Blocking ergosterol synthesis with fluconazole increased the susceptibility against L. fermentum, which was again mitigated by the addition of ergosterol. In accordance, a C. glabrata Derg11 mutant, defective in ergosterol biosynthesis, was highly sensitive to L. fermentum. In conclusion, our analysis indicates an unexpected direct function of ergosterol for C. glabrata proliferation in coculture with L. fermentum.
Project description:Candida glabrata is an important human fungal pathogen leading cause of non-albicans Candida infections. C. glabrata exhibits resistance to key antifungal drugs, rapidly replicates and divides in host macrophages and withstands highly stressful host conditions. This study explores the molecular mechanisms underlying stress adaptations in C. glabrata that contribute to its pathogenicity. Our findings revealed that C. glabrata survives oxidative stress and amino acid starvation more effectively than S. cerevisiae, C. albicans, and C. auris. We noted that Gcn2 kinase and Gcn4 play critical roles in this adaptation as Gcn2 phosphorylates eIF2α and downregulates the global protein translation, activating GCN4. RNA sequencing of WT and gcn4 mutant revealed that GCN4 activation during stress orchestrates the expression of stress-responsive genes vital for survival during amino acid starvation and oxidative stress. Ultimately assisting in the stress adaptative transcriptome. Thus, this study highlights the critical role of the Gcn2–Gcn4 pathway in stress adaptation in C. glabrata.