Biology subjects

Gunde-Cimerman, N.

Publications and source records attributed to Gunde-Cimerman, N..

5 recordsLinked to original sources

bioRxiv2026

Chaotropic Ions Reshape the Cell Wall of the Obligate Halophile Aspergillus atacamensis: Insight from Solid-State NMR

Fungal survival in hypersaline environments requires exceptional adaptation of polysaccharide-based cell walls, yet the molecular principles underlying these adaptations remain largely unknown due to the extreme rarity of obligate halophilic fungi. Aspergillus atacamensis is an obligate halophile and chaotolerant fungus capable of growth at saturating NaCl concentrations and unusually high levels of MgCl2. Here, we used multidimensional solid-state NMR spectroscopy to investigate the molecular organization, hydration, and dynamics of cell wall polysaccharides in intact, uniformly 13C-labeled A. atacamensis cells grown under kosmotropic NaCl and chaotropic MgCl2 conditions. Under NaCl conditions, the rigid cell wall core was dominated by {beta}-1,3-glucan and chitin across all salinities. Hyperosmotic NaCl induced thinner, dehydrated walls with increased polysaccharide mobility. In contrast, MgCl2 exposure resulted in marked remodeling of wall carbohydrates, including the emergence of chitosan, incorporation of mannan into the rigid phase, increased wall thickness, and enhanced hydration and dynamics. Together, these findings reveal fundamentally distinct polysaccharide remodeling strategies in response to kosmotropic versus chaotropic stress and establish a molecular framework for understanding fungal survival in extreme ionic environments. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/700186v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@a38e89org.highwire.dtl.DTLVardef@1e2f7fdorg.highwire.dtl.DTLVardef@71a94org.highwire.dtl.DTLVardef@61f2c4_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSO_LISolid-state NMR reveals salt-dependent remodeling of fungal cell wall polysaccharides C_LIO_LIKosmotropic and chaotropic salts drive distinct cell wall adaptation strategies C_LIO_LINaCl stress promotes dehydration and compaction of the {beta}-1,3-glucan-chitin framework C_LIO_LIMgCl2 induces chitosan emergence and alters mannan organization in the rigid phase C_LIO_LIPolysaccharide hydration and dynamics encode fungal adaptation to extreme environments C_LI

biophysics↗

bioRxiv2025

Genomic rearrangements at the MAT locus suggest reproductive shifts in Rhodotorula yeasts

Transitions from canonical outcrossing to rare, cryptic, or noncanonical reproduction are widespread in fungi, but how mating-type (MAT) systems are reorganized at the genomic and population levels during these shifts remains unclear. The coexistence of sexually reproducing species and putatively asexual lineages makes Rhodotorula a natural comparative system for addressing this question. We analyzed 249 globally sampled strains using a combination of long-read and short-read sequencing. Phylogenomics resolved three major clades and several closely related species complexes. Chromosome-scale assemblies confirmed physical separation of the pheromone/receptor (P/R) and homeodomain (HD) loci, whereas non-random P/R-HD associations revealed constrained tetrapolar inheritance. The P/R locus showed conserved synteny within mating types but extensive structural divergence between A1 and A2 alleles, whereas the HD locus remained compact and conserved. Mating-type distributions varied across clades, with both A1 and A2 present in Clade C, lineage-structured partitioning in Clade B, and pronounced A2 dominance in Clade A. Genome-wide linkage disequilibrium (LD) decay in putatively asexual R. mucilaginosa, although slower than in sexual R. diobovata, was consistent with historical recombination in a species without an observed sexual cycle. Clade A further exhibited deep trans-specific polymorphism of STE3.A2 and relaxed purifying selection, mosaic A2 P/R configurations retaining RHA.A1, A1/A2 and A2/A2 hybrid genomes, and A2-associated gene content beyond MAT loci. In conclusion, our findings underscore the dynamic nature of MAT-locus remodeling in Rhodotorula and establish this genus as a valuable model for investigating transitions from heterothallism toward reproductive strategies less dependent on opposite-type partners.

evolutionary biology↗

bioRxiv2025

Novel insights into the chemodiversity and chemical ecology of the extremophile black yeast Hortaea werneckii, unlocking its potential for compound discovery

Hortaea werneckii is a halotolerant yeast, found in various habitats and which specialized metabolism remains largely unexplored. Moreover, its chemical response to high salinities has not been thoroughly investigated. To address this gap, a large-scale metabolomic study based on HPLC-HRMS/MS was conducted on 64 strains, collected from different habitats worldwide, and cultivated both on saline and non-saline media. The culture media salinity significantly modulated the strains metabolomes, suggesting the yeast exhibits a specific chemical response to high salt concentrations, potentially linked to halotolerance mechanisms. Additionally, the metabolomes were influenced by the ecological origin of the strains, with opportunistic pathogenic isolates producing distinct metabolites. Molecular networking revealed that H. werneckii synthesizes various chemical classes, including potential cytotoxic compounds, making this yeast a potentially interesting source of bioactive compounds. Hortein was detected as dominant and ubiquitous, emerging as a potential chemical marker for the species. This study highlights several compounds of interest, related to the chemical ecology and pathogenicity of H. werneckii. As most of them remain unidentified, future research should prioritize their isolation and identification, to improve our understanding of this extremophile organism and harness its potential in natural product discovery.

microbiology↗

bioRxiv2023

Structural Organization of the Cell Wall of Halophilic Fungi

Halophilic fungi, which thrive in hypersaline habitats and face a range of extreme conditions. These fungal species have gained considerable attention due to their potential applications in harsh industrial processes, such as bioremediation and fermentation under unfavorable conditions of hypersalinity, low water activity, and extreme pH. However, the role of the cell wall in surviving these environmental conditions remains unclear. Here we employ solid-state NMR spectroscopy to compare the cell wall architecture of Aspergillus sydowii across salinity gradients. Analyses of intact cells reveal that A. sydowii cell walls contain a rigid core comprising chitin, {beta}-glucan, and chitosan, shielded by a surface shell composed of galactomannan and galactosaminogalactan. When exposed to hypersaline conditions, A. sydowii enhances chitin biosynthesis and incorporates -glucan to create thick, stiff, and hydrophobic cell walls. Such structural rearrangements enable the fungus to adapt to both hypersaline and salt-deprived conditions, providing a robust mechanism for withstanding external stress. These molecular principles can aid in the optimization of halophilic strains for biotechnology applications.

biophysics↗

bioRxiv2021

The termite fungal cultivar Termitomyces combines diverse enzymes and oxidative reactions for plant biomass conversion

Macrotermitine termites have domesticated fungi in the genus Termitomyces as their primary food source using pre-digested plant biomass. To access the full nutritional value of lignin-enriched plant biomass, the termite-fungus symbiosis requires the depolymerization of this complex phenolic polymer. While most previous work suggests that lignocellulose degradation is accomplished predominantly by the fungal cultivar, our current understanding of the underlying biomolecular mechanisms remains rudimentary. Here, we provide conclusive OMICs and activity-based evidence that Termitomyces partially depolymerizes lignocellulose through the combined actions of high-redox potential oxidizing enzymes (laccases, aryl-alcohol oxidases and a manganese peroxidase), the production of extracellular H2O2 and Fenton-based oxidative degradation, which is catalyzed by a newly described 2-methoxybenzoquinone/hydroquinone redox shuttle system and mediated by secreted chelating dicarboxylic acids. In combination, our approaches reveal a comprehensive depiction of how the efficient biomass degradation mechanism in this ancient insect agricultural symbiosis is accomplished through a combination of white- and brown-rot mechanisms. ImportanceFungus-growing termites have perfected the decomposition of recalcitrant plant biomass to access valuable nutrients by engaging in a tripartite symbiosis with complementary contributions from a fungal mutualist and a co-diversified gut microbiome. This complex symbiotic interplay makes them one of the most successful and important decomposers for carbon cycling in Old World ecosystems. To date, most research has focused on the enzymatic contributions of microbial partners to carbohydrate decomposition. Here we provide genomic, transcriptomic and enzymatic evidence that Termitomyces also employs redox mechanisms, including diverse ligninolytic enzymes and a Fenton-based hydroquinone-catalyzed lignin-degradation mechanism, to break down lignin-rich plant material. Insights into these efficient decomposition mechanisms open new sources of efficient ligninolytic agents applicable for energy generation from renewable sources.

microbiology↗