963 resultados para Virulence factors


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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Members of the Staphylococcus genus, especially Staphylococcus aureus, are the most common pathogens found in hospitals and in community-acquired infections. Some of their pathogenicity is associated with enzyme and toxin production. Until recently, S. aureus was the most studied species in the genus; however, in last few years, the rise of infections caused by coagulase-negative staphylococci has pointed out the need for further studies on virulence factors that have not yet been completely elucidated so as to better characterize the pathogenic potential of this group of microorganisms. Several staphylococcal species produce enterotoxins, a family of related proteins responsible for many diseases, such as the toxic-shock syndrome, septicemia and food poisoning. To this date, 23 different enterotoxin types have been identified besides toxic-shock syndrome toxin-1 (TSST-1), and they can be divided into five phylogenetic groups. The mechanism of action of these toxins includes superantigen activity and emetic properties, which can lead to biological effects of infection. Various methods can detect genes that encode enterotoxins and their production. Molecular methods are the most frequently used at present. This review article has the objective to describe aspects related to the classification, structure and regulation of enterotoxins and toxic-shock syndrome toxin-1 detection methods.

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Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Candida albicans is a common opportunistic, dimorphic human fungal pathogen. One of its virulence factors is the morphological switch between yeasts and hyphal or pseudohyphal forms, which can invade tissues and cause damage. Our studies focus on factors regulating pseudohyphae and epigenetic modifications of C. albicans. Regulating factors of pseudohyphae are aromatic alcohols and high phosphate. At low concentrations, exogenous aromatic alcohols induced pseudohyphae, as did high phosphate. For addressing the pathways involved in inducing pseudohyphae by aromatic alcohols or high phosphate, we used mutants defective in cAMP dependent PKA pathway (efg1/efg1), MAP kinase pathway (cph1/cph1), or both (cph1/cph1/efg1/efg1). These mutants failed to produce either hyphae or pseudohyphae in the presence of aromatic alcohols; but high phosphate still stimulated pseudohyphae. Gcn4, a transcription activator of more than 500 amino acid related genes, is turned-on in response to amino acid starvation. The accumulation of aromatic alcohols sends nitrogen starvation signals, which inhibit eIF2B, which in turn derepresses Gcn4p. High phosphate also induces pseudohyphae by derepressing Gcn4p, although the pathways involved are still unknown. In sum, aromatic alcohols and high phosphate induce pseudohyphae by derepressing Gcn4. In this study we found a novel posttranslational histone modification in C. albicans, which is biotinylation. Western blot and Mass spectrometry techniques were used to find that Histones H2B and H4 were biotinylated at every condition tested such as yeast vs. hyphae, aerobic growth vs. anaerobic growth, rich medium vs. defined medium. In C. albicans lysines K8, K11 in histone H4 and lysines K17, K18, K31 in histone H2B are biotin attachment sites as found using mass spectrometry. Biotin was also found to enhance the germ tube formation of C. albicans. Germ tube formation assays with biotin-starved cells as inoculum showed low percent of germ tubes (1-5%). Addition of biotin to the media showed 100% germ tubes. Biotinylation of histones were not detected from biotin-starved cells. Appendix-A details work related to Farnesol quantification assays in several strains of C.albicans and Ceratocystis ulmi, and growth studies of class E VPS strains of Saccharomyces Cerevisiae. Adviser: Kenneth W. Nickerson

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)