The cell wall structure: developments in diagnosis and treatment of candidiasis

Candidiasis are among the fungal infections the most difficult to diagnose and treat. Research focused on specific fungal components which are absent in the host, such as the cell wall has lead to a better understanding of Candida albicans pathogenicity and clinical impact. The cell wall is responsible for antigenic expression and primary interaction with the host. It is composed mainly of β-glucans, chitin and mannoproteins, which account for the rigidity of the wall and for the fungal morphology. Of these components, mannoproteins might carry a “morphogenetic code” which might modulate the molecular architecture of the cell wall. The features of specific cell wall proteins as part of building blocks to form this structure is revised, and the usefulness of monoclonal antibodies obtained against cell wall components to study those processes, together with their clinical applicability, is discussed

Saccharomyces cerevisiae Rds2 transcription factor involvement in cell wall composition and architecture

Although the cell wall is very important in yeasts, relatively little is known about the relationship between its structure and function. In Saccharomyces cerevisiae, a family of 55 transcription factor proteins unique to fungi, so-called zinc cluster proteins, has been described. Of these, Rds2 has been identified as an activator/inhibitor of gluconeogenesis. However, previous studies have pointed out additional roles for this protein, specifically, in the modulation of cell-wall architecture and drug sensitivity. In this work, evidence regarding the role of Rds2 as a regulator of cell-wall architecture and composition is presented based on phenotypical analysis of the cell walls prepared from a S. cerevisiae Rds2 mutant strain. Analyses of the sensitivity of this rds2Δ mutant to different drugs and to osmotic stress showed that Rds2 is indeed involved in the drug-sensitivity response and plays a role in determining osmotic sensitivity. [Int Microbiol 2008; 11(1): 57-63

The cell wall structure: developments in diagnosis and treatment of candidiasis

Candidiasis are among the fungal infections the most difficult to diagnose and treat. Research focused on specific fungal components which are absent in the host, such as the cell wall has lead to a better understanding of Candida albicans pathogenicity and clinical impact. The cell wall is responsible for antigenic expression and primary interaction with the host. It is composed mainly of b-glucans, chitin and mannoproteins, which account for the rigidity of the wall and for the fungal morphology. Of these components, mannoproteins might carry a “morphogenetic code” which might modulate the molecular architecture of the cell wall. The features of specific cell wall proteins as part of building blocks to form this structure is revised, and the usefulness of monoclonal antibodies obtained against cell wall components to study those processes, together with their clinical applicability, is [email protected]; [email protected]; [email protected]

Comparative genomics of yeast species: new insights into their biology

The genomes of two hemiascomycetous yeasts (Saccharomyces cerevisiae and Candida albicans) and one archiascomycete (Schizosaccharomyces pombe) have been completely sequenced and the genes have been annotated. In addition, the genomes of 13 more Hemiascomycetes have been partially sequenced. The amount of data thus obtained provides information on the evolutionary relationships between yeast species. In addition, the differential genetic characteristics of the microorganisms explain a number of distinctive biological traits. Gene order conservation is observed between phylogenetically close species and is lost in distantly related species, probably due to rearrangements of short regions of DNA. However, gene function is much more conserved along evolution. Compared to S. cerevisiae and S. pombe, C. albicans has a larger number of specific genes, i.e., genes not found in other organisms, a fact that can account for the biological characteristics of this pathogenic dimorphic yeast which is able to colonize a large variety of environments

Comparative genomics of yeast species: new insights into their biology

The genomes of two hemiascomycetous yeasts (Saccharomyces cerevisiae and Candida albicans) and one archiascomycete (Schizosaccharomyces pombe) have been completely sequenced and the genes have been annotated. In addition, the genomes of 13 more Hemiascomycetes have been partially sequenced. The amount of data thus obtained provides information on the evolutionary relationships between yeast species. In addition, the differential genetic characteristics of the microorganisms explain a number of distinctive biological traits. Gene order conservation is observed between phylogenetically close species and is lost in distantly related species, probably due to rearrangements of short regions of DNA. However, gene function is much more conserved along evolution. Compared to S. cerevisiae and S. pombe, C. albicans has a larger number of specific genes, i.e., genes not found in other organisms, a fact that can account for the biological characteristics of this pathogenic dimorphic yeast which is able to colonize a large variety of [email protected]

Saccharomyces cerevisiae Rds2 transcription factor involvement in cell wall composition and architecture

Although the cell wall is very important in yeasts, relatively little is known about the relationship between its structure and function. In Saccharomyces cerevisiae, a family of 55 transcription factor proteins unique to fungi, so-called zinc cluster proteins, has been described. Of these, Rds2 has been identified as an activator/inhibitor of gluconeogenesis. However, previous studies have pointed out additional roles for this protein, specifically, in the modulation of cell-wall architecture and drug sensitivity. In this work, evidence regarding the role of Rds2 as a regulator of cell-wall architecture and composition is presented based on phenotypical analysis of the cell walls prepared from a S. cerevisiae Rds2 mutant strain. Analyses of the sensitivity of this rds2Δ mutant to different drugs and to osmotic stress showed that Rds2 is indeed involved in the drug-sensitivity response and plays a role in determining osmotic sensitivity.Moreno Gimeno, Inmaculada, [email protected] ; Sentandreu Ramon, Rafael, [email protected] ; Valentin Gomez, Eulogio, [email protected]

Analysis of validamycin as a potential antifungal compound against Candida albicans

Validamycin A has been successfully applied in the fight against phytopathogenic fungi. Here, the putative antifungal effect of this pseudooligosaccharide against the prevalent human pathogen Candida albicans was examined. Validamycin A acts as a potent competitive inhibitor of the cell-wall-linked acid trehalase (Atc1p). The estimated MIC50 for the C. albicans parental strain CEY.1 was 500 mg/l. The addition of doses below MIC50 to exponentially growing CEY.1 cells caused a slight reduction in cell growth. A concentration of 1 mg/ml was required to achieve a significant degree of cell killing. The compound was stable as evidenced by the increased reduction of cell growth with increasing incubation time. A homozygous atc1Δ/atc1Δ mutant lacking functional Atc1p activity showed greater resistance to the drug. The antifungal power of validamycin A was limited compared with the drastic lethal action caused by exposure to amphotericin B. The endogenous content of trehalose rose significantly upon validamycin and amphotericin B addition. Neither serum-induced hypha formation nor the level of myceliation recorded in macroscopic colonies were affected by exposure to validamycin A. Our results suggest that, although validamycin A cannot be considered a clinically useful antifungal against C. albicans, its mechanism of action and antifungal properties provide the basis for designing new, clinically interesting, antifungal-related compounds. [Int Microbiol 2013; 16(4):217-225]Keywords: Candida albicans · Rhizoctonia solani · validamycin A · amphotericin B · trehalos

Aislamiento y caracterización de las vesículas extracelulares en Candida albicans

Background : The occurrence of systemic infections due to C. albicans has increased especially in critically ill patients. In fungal infections, secretory mechanisms are key events for disease establishment. Recent findings demonstrate that fungal organisms release many molecular components to the extracellular space in extracellular vesicles. Aims: We develop a method to obtain exosomes from yeast cultures of the Candida albicans . Methods : Yeast strains used in this work were C. albicans SC5314, C. parapsilosis (ATCC 22019) and C. krusei (ATCC 6258). Yeasts were grown at 37.º in liquid YPD medium. The cell cultures were centrifuged and the supernatant filtered through sterile nitrocellulose. Filtrates were concentrated and centrifuged using an ultracentrifuge. The sediment was analyzed by electron microscopy of transmission. Results: The transmission of electron microscopy and nanoparticle tracking analysis confirmed the presence of extracellular vesicles (exosomes) of sizes between 100 and 200 nm and the absence of cellular contaminants. This was ratified by the characterization of proteins performed through the western blot technique, where the absence of cell contamination in the preparations was assessed. Conclusions: The method proves to be highly effective due to the homogeneity and purity of the obtained microvesicles. The protocol developed in this paper proves to be effective for obtaining exosomes of other Candida species, which will allow future studies to determine its protein composition and the role that these vesicles can play.Contexto: La aparición de infecciones sistémicas por C. albicans ha aumentado sobre todo en pacientes graves. En las infecciones fúngicas, los mecanismos de secreción son eventos clave para que el establecimiento de la enfermedad. Hallazgos recientes demuestran que los organismos fúngicos liberan muchos componentes moleculares al espacio extracelular en vesículas extracelulares. Objetivos: Desarrollamos un método para obtener exosomas de cultivos de levadura de Candida albicans . Métodos: Las cepas de levadura que se usaron en este trabajo son C. albicans SC5314, C. parapsilosis (ATCC 22019) y C. krusei (ATCC 6258). Las levaduras se cultivaron a 37.º C en un medio YPD líquido. Los cultivos de células fueron centrifugados y el sobrenadante, filtrado por medio de nitrocelulosa estéril. Los filtrados se concentraron y centrifugaron usando una ultracentrifugadora. El sedimento fue analizado por un microscopio electrónico de transmisión. Resultados: La microscopía electrónica de transmisión y el análisis de nanopartículas confirman la presencia de vesículas extracelulares (exosomas) de un tamaño entre 100 y 200 nm, así como la ausencia de contaminantes celulares. Esto se ratificó mediante la caracterización de proteínas obtenidas por medio de la técnica de Western blot, donde se evaluó la ausencia de contaminación celular en las preparaciones. Conclusiones: El método es altamente eficaz dada la homogeneidad y la pureza de las microvesículas obtenidas. El protocolo desarrollado en este artículo demuestra ser efectivo para obtener exosomas de otras especies Candida , lo que permitirá que en futuros estudios se determine su composición proteica y el papel que estas vesículas pueden desempeñar.Ciencias Experimentale