Fungi are the most ubiquitous eukaryotes widely distributed across various ecological niches and have a high significance in industrial, agricultural, and medicinal pathogenesis. These microbes are constantly exposed to environmental stress and host defenses during infection. The cell wall plays a vital role in protecting the fungus and maintaining the structural integrity of the cell; therefore, it is important to understand the structure, dynamics, and adaptation mechanisms of this organelle. First, we employed solid-state NMR techniques, functional genomics, and biochemical analysis to identify the functionality and diversity of cell wall carbohydrates in 13C-labeled Aspergillus fumigatus and four mutants depleted of major structural polysaccharides. We revealed a rigid inner core of the cell wall formed by tightly associated chitin and α-1,3-glucan, which are embedded in a soft matrix of β-glucans and capped by a mobile outer shell rich in galactosaminogalactan and galactomannan. The distribution of α-1,3-glucan in chemically and dynamically distinct domains supports its dual functionality in structure and pathogenicity. Second, we documented the structural fingerprints of chitin across six Aspergillus, Candida, and Rhizopus species. We discovered that the crystalline structure of chitin exhibits intrinsic heterogeneity that is resistant to antifungal treatment. Third, we discovered the highly conserved carbohydrate core in both conidia and mycelia using Dynamic Nuclear Polarization (DNP) methods. Finally, we characterized the structural responses of a model halophile Aspergillus sydowii continuously exposed to hypersaline conditions, which were found to enhance the biosynthesis of chitin and α-1,3-glucan to form a highly hydrophobic and stiff cell wall to resist external stress. Our findings provide essential structural information of cell wall carbohydrates and their adaptations at the atomic level, which can be used as the target of novel antifungal compounds with broad spectrums and improved efficacy.
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