Xylella fastidiosa is a fastidious, xylem-limited bacterium that causes a range of economically important plant diseases. Here we report the complete genome sequence of X. fastidiosa clone 9a5c, which causes citrus variegated chlorosis--a serious disease of orange trees. The genome comprises a 52.7% GC-rich 2,679,305-base-pair (bp) circular chromosome and two plasmids of 51,158 bp and 1,285 bp. We can assign putative functions to 47% of the 2,904 predicted coding regions. Efficient metabolic functions are predicted, with sugars as the principal energy and carbon source, supporting existence in the nutrient-poor xylem sap. The mechanisms associated with pathogenicity and virulence involve toxins, antibiotics and ion sequestration systems, as well as bacterium-bacterium and bacterium-host interactions mediated by a range of proteins. Orthologues of some of these proteins have only been identified in animal and human pathogens; their presence in X. fastidiosa indicates that the molecular basis for bacterial pathogenicity is both conserved and independent of host. At least 83 genes are bacteriophage-derived and include virulence-associated genes from other bacteria, providing direct evidence of phage-mediated horizontal gene transfer.

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This study provides several pieces of evidence indicating that 3F6-Ag, identified by monoclonal antibody (MAb) 3F6 as a stage-specific glycoprotein of approximately 82 kDa on the surface of metacyclic trypomastigotes of different Trypanosoma cruzi strains, promotes the entry of parasites into host cells through a ligand-receptor type interaction. First, invasion of Vero cells by metacyclic trypomastigotes of both CL and Tulahuen strains was significantly inhibited by MAb 3F6 or its Fab fragments. Second, purified 3F6-Ag bound to Vero cells in a dose-dependent and saturable fashion. Third, soluble 3F6-Ag reduced the infection of Vero cells by metacyclic forms of CL and Tulahuen strains by 90 to 97 and 50%Yo, respectively. Unrelated proteins, as well as extracellular matrix components, such as heparan sulfate and collagen, had no effect. Our studies also show that in the Tulahuen strain, 10D8-Ag, a 35/50-kDa glycoprotein identified by MAb 10D8, participates in target cell invasion, confirming previous observations, but the variant form of 10D8-Ag expressed by highly invasive CL strain metacyclic trypomastigotes appears to be irrelevant. Overall, our results indicate that the

The anti-Trypanosoma cruzi activity of natural products isolated from Azorella compacta was evaluated, with particular emphasis on their effect against intracellular amastigotes. Five diterpenoids from A. compacta derived from mulinane and azorellane were isolated and identified. Only two products, named azorellanol (Y-2) and mulin-11,3-dien-20-oic acid (Y-5) We evaluated the effect of diterpenoids against intracellular T. cruzi forms by immunofluorescent identification of a specific membrane molecular marker (Ssp-4 antigen) of the T. cruzi amastigote forms. The accuracy and reproducibility of the measurements were found to be outstanding when examined by confocal microscopy.

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The surface glycoprotein gp82, expressed in the insect-stage metacyclic trypomastigotes of Trypanosoma cruzi, has been implicated in mammalian cell invasion. Here we have characterized the cell adhesion site of gp82 by using recombinant proteins and synthetic peptides based on gp82. The recombinant protein Del-4/8, lacking 65 amino acids of gp82 central domain (at positions 257 to 321), was virtually devoid of cell-binding activity and lacked the ability to inhibit parasite invasion, in contrast to J18, the construct containing the full-length gp82 sequence (amino acids 1 to 516). Constructs with shorter deletions, i.e., Del-4 (deleted from 257 to 271) and Del-8 (deleted from 293 to 321), bound to target cells to a significantly lesser degree than did J18. The sites deleted in recombinant proteins Del-4 and Del-8 contained acidic amino acids critical for cell adhesion. Thus, the cell-binding capacity of protein Del-E/D, lacking the glutamic acid (259/260) and aspartic acid (303/304) pairs, was negligible, as was its capacity to inhibit parasite internalization. Of a set of synthetic peptides spanning the gp82 central domain, a 22-mer hybrid peptide, p4/8, formed by two noncontiguous sequences (at positions 257 to 273 and 302 to 306) and containing the four acidic residues, competed with the binding of J18 protein to target cells and significantly inhibited (ϳ60%) the penetration of parasites. This peptide, generated by the juxtaposition of sequences that are separated by a hydrophobic stretch in the linear molecule, appears to be mimicking a conformation-dependent cell-binding site of gp82. Experiments of antibody competition with a set of 20-mer overlapping peptides mapped the epitope for 3F6, a monoclonal antibody directed to gp82 that inhibits parasite invasion, to the sequence represented by peptide p3 (244 to 263), which has a partial overlap with the cell adhesion site.

RESUMEN Llayta es el nombre asignado a la biomasa seca de macrocolonias de una cianobacteria filamentosa, clasificada como Nostoc sp. Llayta crece en humedales andinos de Sudamérica y ha sido considerada como un ingrediente alimenticio desde tiempos precolombinos. Este estudio pretende contribuir a la definición de la calidad nutritiva de la Llayta, proporcionando información sobre su composición bioquímica e identificar aspectos críticos de interés toxicológico. Los resultados mostraron que el 60% del total de sus aminoácidos son indispensables, contenía un 2% de lípidos totales, 32% del total de ácidos grasos eran poliinsaturados, la vitamina E fue la más abundante (4,3 mg%), el contenido de polifenoles totales es 64 mg equivalentes de ácido gálico, su actividad antioxidante es 17,4 μmoles equivalentes de Trolox, la fibra total fue el 56% del peso seco y presentó un contenido promedio de arsénico total de 9,2 ± 5,4 ppm. Esta cianobacteria no es productora de microcistina, por lo que las colonias de la Llayta podrían considerarse inocua para el consumo humano.