Palynological evidence of post-catastrophe fungal proliferation after global calamities has been found for the Permian-Triassic and Cretaceous-Paleogene (K/Pg) extinction events. However, unlike the globally documented post-Permian fungal bloom, evidence of a post-Cretaceous event has previously been limited to a single site in New Zealand. Our analysis of a K/Pg boundary section from the Denver Basin in Colorado revealed a fungal proliferative spike occurring immediately after the Chicxulub impact. The discovery of a post-impact fungal bloom in North America corroborates the New Zealand finding and supports the interpretation that this was a global phenomenon. We also identified a prolonged interval of elevated fungal abundance in the Late Cretaceous, dating to approximately 30,000-10,000 years before the impact, temporally correlated to a period of climatic cooling at the site and intriguingly coincident with the Poladpur phase of the Deccan Traps. Taken together with reports of fungal expansion following prior global calamities, these findings indicate that fungi can often flourish in the aftermath of ecosystem-level collapse. Given the capacity of fungi to cause disease in both plants and animals, the occurrence of fungal proliferative events has major potential implications for the recovery of surviving species after global cataclysms.

Among the many natural biomaterials for which information on atomic-level structure and reorientational motion can offer essential clues to function, insoluble multi-component composites with limited degrees of order are among the most challenging to study. Despite its limited sensitivity, solid-state NMR (ssNMR) is often the technique of choice to ferret out these details in carbon- and nitrogen-rich materials: this spectroscopic approach can probe many biomaterials in their native or near-native states, either with or without the introduction of stable NMR-active isotopes, or with the assistance of dynamic nuclear polarization technology. During a span of close to four decades, such research targets and ssNMR approaches have been exemplified by insects, a diverse and evolutionarily agile group of organisms with global impacts that include ecology, agriculture, and human disease. In this short review, we present case studies on insect cuticles that range from protective exoskeletons and egg capsules to the wing structures that enable flight and showcase nature's awe-inspiring beauty, highlighting the use of ssNMR spectroscopy to profile chemical composition, elucidate macromolecular architecture, and monitor metabolic development in these fascinating biological assemblies. © 2024 Elsevier Inc.

Microbial polysaccharide characterization requires purification that often involves detergent precipitation and lyophilization. Here we examined physicochemical changes following lyophilization of Cryptococcus neoformans exopolysaccharide (EPS). Solution 1H Nuclear Magnetic Resonance (NMR) reveals significant anomeric signal attenuation following lyophilization of native EPS while 1H solid-state Nuclear Magnetic Resonance (ssNMR) shows few changes, suggesting diminished molecular motion and consequent broadening of 1H NMR polysaccharide resonances. 13C ssNMR, dynamic light scattering, and transmission electron microscopy show that, while native EPS has rigid molecular characteristics and contains small, loosely packed polysaccharide assemblies, lyophilized and resuspended EPS is disordered and contains larger dense aggregates, suggesting that structural water molecules in the interior of the polysaccharide assemblies are removed during extensive lyophilization. Importantly, mAbs to C. neoformans polysaccharide bind native EPS more strongly than lyophilized EPS. Together, these observations argue for caution when interpreting the biological and immunological attributes of polysaccharides that have been lyophilized to dryness.

Melanin is a major virulence factor in pathogenic fungi that enhances the ability of fungal cells to resist immune clearance. Cryptococcus neoformans is an important human pathogenic fungus that synthesizes melanin from exogenous tissue catecholamine precursors during infection, but the type of melanin made in cryptococcal meningoencephalitis is unknown. We analyzed the efficacy of various catecholamines found in brain tissue in supporting melanization using animal brain tissue and synthetic catecholamine mixtures reflecting brain tissue proportions. Solid-state NMR spectra of the melanin pigment produced from such mixtures yielded more melanin than expected if only the preferred constituent dopamine had been incorporated, suggesting uptake of additional catecholamines. Probing the biosynthesis of melanin using radiolabeled catecholamines revealed that C. neoformans melanization simultaneously incorporated more than one catecholamine, implying that the pigment was polytypic in nature. Nonetheless, melanin derived from individual or mixed catecholamines had comparable ability to protect C. neoformans against ultraviolet light and oxidants. Our results indicate that melanin produced during infection differs depending on the catecholamine composition of tissue and that melanin pigment synthesized in vivo is likely to accrue from the polymerization of a mixture of precursors. From a practical standpoint, our results strongly suggest that using dopamine as a polymerization precursor is capable of producing melanin pigment comparable to that produced during infection. On a more fundamental level, our findings uncover additional structural complexity for natural cryptococcal melanin by demonstrating that pigment produced during human infection is likely to be composed of polymerized moieties derived from chemically different precursors.

Melanin is a major virulence factor in pathogenic fungi that enhances the ability of fungal cells to resist immune clearance. Cryptococcus neoformans is an important human pathogenic fungus that synthesizes melanin from exogenous tissue catecholamine precursors during infection, but the type of melanin made in cryptococcal meningoencephalitis is unknown. We analyzed the efficacy of various catecholamines found in brain tissue in supporting melanization using animal brain tissue and synthetic catecholamine mixtures reflecting brain tissue proportions. Solid-state NMR spectra of the melanin pigment produced from such mixtures yielded more melanin than expected if only the preferred constituent dopamine had been incorporated, suggesting uptake of additional catecholamines. Probing the biosynthesis of melanin using radiolabeled catecholamines revealed that C. neoformans melanization simultaneously incorporated more than one catecholamine, implying that the pigment was polytypic in nature. Nonetheless, melanin derived from individual or mixed catecholamines had comparable ability to protect C. neoformans against ultraviolet light and oxidants. Our results indicate that melanin produced during infection differs depending on the catecholamine composition of tissue and that melanin pigment synthesized in vivo is likely to accrue from the polymerization of a mixture of precursors. From a practical standpoint, our results strongly suggest that using dopamine as a polymerization precursor is capable of producing melanin pigment comparable to that produced during infection. On a more fundamental level, our findings uncover additional structural complexity for natural cryptococcal melanin by demonstrating that pigment produced during human infection is likely to be composed of polymerized moieties derived from chemically different precursors. © 2021 THE AUTHORS. Published by Elsevier Inc on behalf of American Society for Biochemistry and Molecular Biology. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

In recent decades, Galleria mellonella (Lepidoptera: Pyralidae) have emerged as a model system to explore experimental aspects of fungal pathogenesis. The benefits of the G. mellonella model include being faster, cheaper, higher throughput and easier compared with vertebrate models. Additionally, as invertebrates, their use is subject to fewer ethical and regulatory issues. However, for G. mellonella models to provide meaningful insight into fungal pathogenesis, the G. mellonella-fungal interactions must be comparable to mammalian-fungal interactions. Indeed, as discussed in the review, studies suggest that G. mellonella and mammalian immune systems share many similarities, and fungal virulence factors show conserved functions in both hosts. While the moth model has opened novel research areas, many comparisons are superficial and leave large gaps of knowledge that need to be addressed concerning specific mechanisms underlying G. mellonella-fungal interactions. Closing these gaps in understanding will strengthen G. mellonella as a model for fungal virulence in the upcoming years. In this review, we provide comprehensive comparisons between fungal pathogenesis in mammals and G. mellonella from immunological and virulence perspectives. When information on an antifungal immune component is unknown in G. mellonella, we include findings from other well-studied Lepidoptera. We hope that by outlining this information available in related species, we highlight areas of needed research and provide a framework for understanding G. mellonella immunity and fungal interactions.