Biology subjects

Cordero, R. J.

Publications and source records attributed to Cordero, R. J..

9 recordsLinked to original sources

bioRxiv2024

Dietary L-3,4-dihydroxyphenylalanine (L-DOPA) augments cuticular melanization in Anopheles mosquitos while reducing their lifespan and malaria parasite burden

L-3,4-dihydroxyphenylalanine (L-DOPA), a naturally occurring tyrosine derivative, is prevalent in environments that include mosquito habitats, potentially serving as part of their diet. Given its role as a precursor for melanin synthesis we investigate the effect of dietary L-DOPA on mosquito physiology and immunity to Plasmodium falciparum and Cryptococcus neoformans infection. Dietary L-DOPA is incorporated into mosquito melanin via a non-canonical pathway and has a profound transcriptional effect associated with enhanced immunity, increased pigmentation, and reduced lifespan. Increased melanization results in an enhanced capacity to absorb electromagnetic radiation that affects mosquito temperatures. Bacteria in the mosquito microbiome act as sources of dopamine, a substrate for melanization. Our results illustrate how an environmentally abundant amino acid analogue can affect mosquito physiology and suggest its potential usefulness as an environmentally friendly vector control agent to reduce malaria transmission, warranting further research and field studies.

microbiology↗

bioRxiv2023

Neutron Scattering Analysis of the Cryptococcus neoformans Polysaccharide Reveals Solution Rigidity and Repeating Fractal-like Structural Patterns

ABSTRACTCryptococcus neoformans is a fungal pathogen that can cause life-threatening brain infections in immunocompromised individuals. Unlike other fungal pathogens, it possesses a protective polysaccharide capsule that is crucial for its virulence. During infections, Cryptococcus cells release copious amounts of extracellular polysaccharides (exo-PS) that interfere with host immune responses. Both exo-PS and capsular-PS play pivotal roles in Cryptococcus infections and serve as essential targets for disease diagnosis and vaccine development strategies. However, understanding their structure is complicated by their polydispersity, complexity, sensitivity to sample isolation and processing, and scarcity of methods capable of isolating and analyzing them while preserving their native structure. In this study, we employ small-angle neutron scattering (SANS) and ultra-small angle neutron scattering (USANS) for the first time to investigate both fungal cell suspensions and extracellular polysaccharides in solution. Our data suggests that exo- PS in solution exhibits collapsed chain-like behavior and demonstrates mass fractal properties that indicate a relatively condensed pore structure in aqueous environments. This observation is also supported by scanning electron microscopy (SEM). The local structure of the polysaccharide is characterized as a rigid rod, with a length-scale corresponding to 3 to 4 repeating units. This research not only unveils insights into exo-PS and capsular-PS structures but also demonstrates the potential of USANS for studying changes in cell dimensions and the promise of contrast variation in future neutron scattering studies.

biophysics↗

bioRxiv2022

Melaninization Reduces Cryptococcus neoformans Susceptibility to Mechanical Stress

Melanin is a complex pigment found in various fungal species that is associated with a multitude of protective functions against environmental stresses. In Cryptococcus neoformans, melanin is synthesized from exogenous substrate and deposited in the cell wall. Although melanin is often cited as a protector against mechanical stress, there is a paucity of direct experimental data supporting this claim. To probe whether melanin enhances cellular strength, we used ultrasonic cavitation and French pressure cell press to stress cryptococcal cells and then measured changes in cellular morphology and survival for melanized and non-melanized C. neoformans. Melanized yeast exhibited lower rates of fragmentation and lower decreases in cell area when compared to non-melanized yeast after sonication and French press conditions. Our results indicate that melanization protects against some of the morphologic changes initiated by mechanical energy derived from either sonic cavitation or French press, thus supporting the notion that this pigment provides mechanical strength to fungal cell walls. ImportanceMelanin has been shown from prior experiments in microbiology to be associated with protection against environmental stressors and has often been cited as being associated with mechanical stress protection. However, there is a lack of direct experimentation to confirm this claim. By examining the response of melanized and non-melanized C. neoformans to sonication and French press, we report differences in outcomes dependent not only based on melanization status but also culture age. Such findings have important implications in the design and interpretation of laboratory experiments involving C. neoformans. In addition, uncovering some of melanins mechanical properties promotes further research into fungal melanins applications in healthcare and industry.

microbiology↗

bioRxiv2021

Cryptococcus neoformans capsule regrowth experiments reveal dynamics of enlargement and architecture

The polysaccharide capsule of fungal pathogen Cryptococcus neoformans is a critical virulence factor that has historically evaded characterization. Polysaccharides remain attached to the cell as capsular polysaccharide (CPS) or are shed into the surroundings in the form of exopolysaccharide (EPS). While a great deal of study has been done examining the properties of EPS, far less is known about CPS. In this work, we detail the development of new physical and enzymatic methods for the isolation of CPS which can be used to explore the architecture of the capsule and removed capsular material. Sonication and glucanex digestion yield soluble CPS preparations, while French Press and modified glucanex digestion plus vortexing remove the capsule and cell wall producing polysaccharide aggregates that we call capsule ghosts. The existence of capsule ghosts implies an inherent organization that allows it to exist independent of the cell wall surface. As sonication and glucanex digestion were noncytotoxic, it was possible to observe the cryptococcal cells rebuilding their capsule, revealing new insights into capsule architecture and synthesis consistent with a model in which the capsule is assembled from smaller polymers, which are then assemble into larger ones. ImportanceCharacterization of the cryptococcal polysaccharide capsule relies on methods of isolation for its in vitro study. This study demonstrates that the capsule is susceptible to physical and enzymatic removal. The application of new methods yields insights into the anatomy, modular nature, and architecture of the capsule with both soluble CPS preparations and capsule ghosts. Together these insights inform on a long-standing debate modeling capsular assembly wherein our data shows that the capsule is assembled by smaller polymers added distally rather than by proximal addition or by polymers spanning the entire capsule radius.

microbiology↗

bioRxiv2020

Antifungal activity of 2,3-diphenyl-2,3-dihydro-1,3-thiaza-4-ones against two human pathogenic fungi

Invasive fungal diseases are prevalent in immunocompromised individuals in whom current therapies often provide suboptimal results. Additionally, the increased resistance to the available antifungal drugs necessitates a search for new compounds. This study reports the antifungal activity of six 5-, 6-, and 7-membered 2,3-diphenyl-2,3-dihydro-1,3-thiaza-4-ones against Lomentospora prolificans and Cryptococcus neoformans. Our data showed that some of the compounds tested had a low MIC and damage on the cell surface of the tested fungal species.

microbiology↗

bioRxiv2020

Hypothermia is a characteristic of the fungal kingdom

Fungi play essential roles in global ecology and economy, but their thermal biology is widely unknown. Mushrooms were previously noticed to be colder than surrounding air via evaporative cooling or evapotranspiration. Here we applied infrared imaging to reveal that not just mushrooms, but also molds and yeasts maintain colder temperatures than their surroundings via evapotranspiration. On average, fungal specimens are ~2.5 {degrees}C colder than the surrounding temperature. The relatively cold temperature of mushrooms can be observed throughout the whole fruiting process and at the level of mycelium. The mushrooms hymenium appeared the coldest and different areas of the Pleurotus ostreatus mushroom appear to dissipate heat differently. Evapotranspiration in yeast and mold biofilms can be measured from the accumulation of condensed water droplets above biofilms; which is significantly higher than the surrounding agar. We also present a mushroom-based air-cooling system (MycoCooler) capable of passively reducing the temperature of a closed compartment by approximately 10 {degrees}C in 25 minutes. These findings suggest that the fungal kingdom is characteristically cold. Since fungi make up ~2% of Earth biomass, their evapotranspiration may contribute to planetary temperatures in local environments. This study present new research avenues in fungal biology, biomedicine, microclimate, and sustainable energy.

microbiology↗

bioRxiv2019

The structural unit of melanin in the cell wall of the fungal pathogen Cryptococcus neoformans

Melanins are synthesized macromolecules that are found in all biological kingdoms. These pigments have a myriad of roles that range from microbial virulence to key components of the innate immune response in invertebrates. Melanins also exhibit unique properties with potential applications in physics and material sciences, ranging from electrical batteries to novel therapeutics. In the fungi, melanins such as eumelanins, are components of the cell wall that provide protection against biotic and abiotic elements. Elucidation of the smallest fungal cell wall-asociated melanin unit that serves as a building block is critical to understand the architecture of these polymers, its interaction with surrounding components, and their functional versatility. In this study, we used isopycnic gradient sedimentation, NMR, EPR, high-resolution microscopy, and proteomics to analyze the melanin in the cell wall of the human pathogenic fungus Cryptococcus neoformans. We observed that melanin is assembled into the cryptococcal cell wall in spherical structures of [~]200 nm in diameter, termed melanin granules, which are in turn composed of nanospheres of [~]30 nm in diameter, the fungal melanosomes. We noted that melanin granules are closely associated with proteins that may play critical roles in the fungal melanogenesis and the supramolecular structure of this polymer. Using this structural information, we propose a model for C. neoformans melanization that is similar to the process used in animal melanization and is consistent with the phylogenetic relatedness of the fungal and animal kingdoms.

microbiology↗

bioRxiv2018

The buoyant cell density of Cryptococcus neoformans is affected by capsule size

Cryptococcus neoformans is an environmental pathogenic fungus with a worldwide geographical distribution that is responsible for hundreds of thousands human cryptococcosis cases each year. During infection, the yeast undergoes a morphological transformation involving capsular enlargement that increases microbial volume. To understand the factors that play a role in environmental dispersal of C. neoformans and C. gatii we evaluated the buoyant cell density of Cryptococcus using Percoll isopycnic gradients. We found differences in the buoyant cell density of strains belonging to C. neoformans and C. gatti species complexes. The buoyant cell density of C. neoformans strains varied depending on growth medium conditions. In minimal medium, the cryptococcal capsule made a major contribution to the buoyant cell density such that cells with larger capsules had lower density than those with smaller capsules. Removing the capsule, both by chemical or mechanical methods, decreased the C. neoformans cell density. Melanization of the C. neoformans cell wall, which also contributes to virulence, produced a small but consistent increase in cell density. C. neoformans sedimented much slower in seawater as its density approached the density of water. Our results suggest a new function for the capsule whereby it can function as a flotation device to facilitate transport and dispersion in aqueous fluids.

microbiology↗

bioRxiv2018

The capsule of Cryptococcus neoformans modulates phagosomal pH through its acid-base properties

Phagosomal acidification is a critical cellular mechanism for the inhibition and killing of ingested microbes by phagocytic cells. The acidic environment activates microbicidal proteins and creates an unfavorable environment for the growth of many microbes. Consequently, numerous pathogenic microbes have developed strategies for countering phagosomal acidification through various mechanisms that include interference with phagosome maturation. The human pathogenic fungus Cryptococcus neoformans resides in acidic phagosome after macrophage ingestion that actually provides a favorable environment for replication since the fungus replicates faster at acidic pH. We hypothesized that the glucuronic acid residues in the capsular polysaccharide had the capacity to affect phagosome acidity through their acid-base properties. A ratiometric fluorescence comparison of imaged phagosomes containing C. neoformans to those containing beads showed that the latter were significantly more acidic. Similarly, phagosomes containing non-encapsulated C. neoformans cells were more acidic than those containing encapsulated cells. Acid-base titrations of isolated C. neoformans polysaccharide revealed that it behaves as a weak acid with maximal buffering capacity around pH 4-5. We interpret these results as indicating that the glucuronic acid residues in the C. neoformans capsular polysaccharide can buffer phagosomal acidification. Interference with phagosomal acidification represents a new function for the cryptococcal capsule in virulence and suggests the importance of considering the acid-base properties of microbial capsules in the host-microbe interaction for other microbes with charged residues in their capsules.\n\nImportanceCryptococcus neoformans is the causative agent of cryptococcosis, a devastating fungal disease that affects thousands of individuals worldwide. This fungus has the capacity to survive inside phagocytic cells, which contributes to persistence of infection and dissemination. One of the major mechanisms of host phagocytes is to acidify the phagosomal compartment after ingestion of microbes. This study shows that the capsule of C. neoformans can interfere with full phagosomal acidification by serving as a buffer.

microbiology↗