Occurrence of killer Candida glabrata clinical isolates

"In this work we characterized the occurrence of killer activity in 64 Candida glabrata clinical isolates under different conditions. We found that only 6.25 % of the clinical isolates tested were positive for killer activity against a Saccharomyces cerevisiae W303 sensitive strain. Sensitivity of killer activity to different values of pH and temperatures was analyzed. We found that the killer activity presented by all isolates was resistant to every pH and temperature tested, although optimal activity was found at a range of pH values from 4 to 7 and at 37ºC. We did not observe extrachromosomal genetic elements associated with killer activity in any of the positive C. glabrata isolates. The killer effect was due to a decrease in viability and DNA fragmentation in sensitive yeast.

Estudio etnobotánico y evaluación citotóxica de extractos etanólicos de plantas de uso medicinal en Tlalchi, Ixhuacán de los Reyes, Veracruz, México

Las plantas medicinales son especies vegetales que contienen sustancias empleadas con propósitos terapéuticos y pueden servir de precursores para la síntesis de nuevos fármacos. En el presente trabajo se realizó un estudio etnobotánico y toxicológico de plantas de uso medicinal de Tlalchi, Ixhuacán de los Reyes en el estado de Veracruz, México. Se registraron 22 especies distribuidas en 17 familias, destacando Asteraceae con el mayor número de frecuencia. Las especies seleccionadas fueron Solanum nigrum, Bidens pilosa, Tithonia diversifolia, Commelina diffusa, Justicia pectoralis, y Aldama dentata. Se realizó un análisis fitoquímico preliminar de las mismas, donde se obtuvo la presencia de alcaloides, flavonoides, triterpenos y saponinas. Solanum nigrum tuvo mayor toxicidad de 51.72 µg/mL. Esta última especie tuvo toxicidad en la línea celular HeLa, obteniendo una reducción del 50% de viabilidad celular a partir de las 24 h. S. nigrum podría ser un potencial agente anti-proliferativo en este tipo de células

yKu70/yKu80 and Rif1 regulate silencing differentially at telomeres in Candida glabrata

"Candida glabrata, a common opportunistic fungal pathogen, adheres efficiently to mammalian epithelial cells in culture. This interaction in vitro depends mainly on the adhesin Epa1, one of a large family of cell wall proteins. Most of the EPA genes are located in subtelomeric regions, where they are transcriptionally repressed by silencing. In order to better characterize the transcriptional regulation of the EPA family, we have assessed the importance of C. glabrata orthologues of known regulators of subtelomeric silencing in Saccharomyces cerevisiae. To this end, we used a series of strains containing insertions of the reporter URA3 gene within different intergenic regions throughout four telomeres of C. glabrata. Using these reporter strains, we have assessed the roles of SIR2, SIR3, SIR4, HDF1 (yKu70), HDF2 (yKu80), and RIF1 in mediating silencing at four C. glabrata telomeres. We found that, whereas the SIR proteins are absolutely required for silencing of the reporter genes and the native subtelomeric EPA genes, the Rif1 and the Ku proteins regulate silencing at only a subset of the analyzed telomeres. We also mapped a cis element adjacent to the EPA3 locus that can silence a reporter gene when placed at a distance of 31 kb from the telomere. Our data show that silencing of the C. glabrata telomeres varies from telomere to telomere. In addition, recruitment of silencing proteins to the subtelomeres is likely, for certain telomeres, to depend both on the telomeric repeats and on particular discrete silencing elements.