Biology subjects

Frases, S.

Publications and source records attributed to Frases, S..

3 recordsLinked to original sources

bioRxiv2021

Extracellular vesicles regulate yeast growth, biofilm formation, and yeast-to-hypha differentiation in Candida albicans

The ability to undergo morphological changes during adaptation to distinct environments is exploited by Candida albicans and has a direct impact on virulence. In this study, we investigated the influence of fungal extracellular vesicles (EVs) during yeast growth, biofilm formation, and morphogenesis in C. albicans. Addition of C. albicans EVs (Ca EVs) to the culture medium positively affected yeast growth. Using crystal violet staining and scanning electron microscopy (SEM), we demonstrated that Ca EVs inhibited biofilm formation by C. albicans in vitro. By time-lapse microscopy and SEM, we showed that Ca EV-treatment stops filamentation promoting pseudohyphae formation with multiple sites for yeast budding. The ability of Ca EVs to regulate dimorphism was further compared to EVs isolated from different C. albicans strains, Saccharomyces cerevisiae, and Histoplasma capsulatum. Ca EVs from distinct strains robustly inhibited yeast-to-hyphae differentiation with morphological changes occurring in less than 4 hours. A minor inhibitory effect was promoted by EVs from S. cerevisiae and H. capsulatum only after 24 hours of incubation. The inhibitory effect of Ca EVs was promoted by a combination of lipid compounds identified by gas chromatography-tandem mass spectrometry analysis as sesquiterpenes, diterpenes, and fatty acids. Remarkably, Ca EVs were also able to reverse filamentation, transforming hyphal growth to yeast forms. Transcriptomic analysis demonstrated that treatment with Ca EVs modified the expression of more than 300 genes. The most effectively upregulated pathways were related to DNA metabolism. The downregulated genes were mostly associated with extracellular and adhesion proteins. Finally, yeast cells treated with Ca EVs for 24 hours lost their agar invasive ability and were avirulent when inoculated in Galleria mellonella larvae. In summary, our results indicate that fungal EVs can profoundly modify C. albicans growth and regulate yeast-to-hypha differentiation inhibiting biofilm formation and virulence.

microbiology↗

bioRxiv2020

Let it bud: an ultrastructural study of Cryptococcus neoformans surface during budding events

Cryptococcus neoformans is a fungal pathogen that causes life-threatening infections in immunocompromised individuals. It is surrounded by three concentric structures that separate the cell from the extracellular space: the plasma membrane, the cell wall and the polysaccharide capsule. Although several studies have revealed the chemical composition of these structures, little is known about their ultrastructural organization and remodeling during C. neoformans budding event. Here, by combining the state-of-the-art in light and electron microscopy techniques we describe the morphological remodeling that occurs synergistically among the capsule, cell wall and plasma membrane during budding in C. neoformans. Our results show that the cell wall deforms to generate a specialized budding region at one of the cells poles. This region subsequently begins to break into layers that are slightly separated from each other and with thick tips. We also observe a reduction in density of the capsular polysaccharide around these specialized regions. Daughter cells present a distinct spatial organization, with polysaccharide fibers aligned in the direction of budding. In addition, to control the continuous openings between mother and daughter cells, the latter developed a strategy to shield themselves by forming multilamellar membrane structures in conjunction with their capsules. Together, our findings provide compelling ultrastructural evidence for a dynamic C. neoformans surface remodeling during budding and may have important implications for future studies exploring these remodeled specialized regions as drug-targets against cryptococcosis.

microbiology↗

bioRxiv2020

Membrane Elastic Properties During Neural Progenitor/Neural Stem Cell Differentiation

Neural stem cells differentiate into several cell types that display distinct functions. However, little is known about how cell surface mechanics vary during the differentiation process. Here, by precisely measuring membrane tension and bending modulus, we map their variations and correlate them with changes in cell morphology along differentiation into neurons, astrocytes and oligodendrocytes. Both neurons and undifferentiated cells reveal a decrease in membrane tension over the first hours of differentiation followed by stabilization, with no change in bending modulus. Astrocytes membrane tension initially decreases and then increases after 72h, accompanied by consolidation of GFAP expression and striking actin reorganization, while bending modulus increases following observed alterations. For oligodendrocytes, the changes in membrane tension are less abrupt over the first hours but their values subsequently decrease, correlating with a shift from O4 to MBP expressions and a remarkable actin reorganization, while bending modulus remains constant. Oligodendrocytes at later differentiation stages show membrane vesicles with similar membrane tension but higher bending modulus as compared to the cell surface. Altogether, our results display an entire spectrum of how membrane elastic properties are varying, contributing to a better understanding of neural stem cell differentiation from a mechanobiological perspective.

biophysics↗