Cell wall biogenesis in a double chitin synthase mutant (chsG-/chsE-) of Aspergillus fumigatus.

Previous studies (Aufauvre-Brown et al., 1997; Mellado et al., 1996a,b ) have shown that only two genes of the Aspergillus fumigatus chitin synthase family, chsG and chsE, play a role in the morphogenesis of this fungal species.

A new experimental murine aspergillosis model to identify strains of Aspergillus fumigatus with reduced virulence.

Experimental animals are an obligate screen to investigate microorganism pathogenicity. Numerous animal models have been used to analyse the virulence of the opportunistic human pathogen Aspergillus fumigatus but none of the experimental models used previously have been satisfactory. This report discuss these models and presents a murine model of pulmonary aspergillosis that is very easy and the most adapted to compare the pathogenicity of A.

Proteome analysis of Aspergillus fumigatus identifies glycosylphosphatidylinositol-anchored proteins associated to the cell wall biosynthesis.

Previous studies in Aspergillus fumigatus (Mouyna I., Fontaine T., Vai M.

Molecular organization of the alkali-insoluble fraction of Aspergillus fumigatus cell wall.

Physical and biological properties of the fungal cell wall are determined by the composition and arrangement of the structural polysaccharides. Cell wall polymers of fungi are classically divided into two groups depending on their solubility in hot alkali. We have analyzed the alkali-insoluble fraction of the Aspergillus fumigatus cell wall, which is the fraction believed to be responsible for fungal cell wall rigidity.

Glycosylphosphatidylinositol-anchored glucanosyltransferases play an active role in the biosynthesis of the fungal cell wall.

A novel 1,3-beta-glucanosyltransferase isolated from the cell wall of Aspergillus fumigatus was recently characterized. This enzyme splits internally a 1,3-beta-glucan molecule and transfers the newly generated reducing end to the non-reducing end of another 1, 3-beta-glucan molecule forming a 1,3-beta linkage, resulting in the elongation of 1,3-beta-glucan chains. The GEL1 gene encoding this enzyme was cloned and sequenced.

Cloning and disruption of the antigenic catalase gene of Aspergillus fumigatus.

Aspergillus fumigatus possesses two catalases (described as fast and slow on the basis of their electrophoretic mobility). The slow catalase has been recognized as a diagnostic antigen for aspergillosis in immunocompetent patients. The antigenic catalase has been purified.

Differential patterns of activity displayed by two exo-beta-1,3-glucanases associated with the Aspergillus fumigatus cell wall.

Two exo-beta-1,3-glucanases (herein designated exoG-I and exoG-II) were isolated from the cell wall autolysate of the filamentous fungus Aspergillus fumigatus and purified by ion-exchange, hydrophobic-interaction, and gel filtration chromatographies. Molecular masses estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration chromatography were 82 kDa for the monomeric exoG-I and 230 kDa for the dimeric exoG-II. exoG-I and exoG-II were glycosylated, and N glycans accounted, respectively, for 2 and 44 kDa.

Biochemical and antigenic characterization of a new dipeptidyl-peptidase isolated from Aspergillus fumigatus.

A novel dipeptidyl-peptidase (DPP V) was purified from the culture medium of Aspergillus fumigatus. This is the first report of a secreted dipeptidyl-peptidase. The enzyme had a molecular mass of 88 kDa and contained approximately 9 kDa of N-linked carbohydrate.

Purification and characterization of an endo-1,3-beta-glucanase from Aspergillus fumigatus.

An endo-1,3-beta-glucanase was purified from a cell wall autolysate of Aspergillus fumigatus. This beta-glucanase activity was associated with a glycosylated 74-kDa protein. Using a sensitive colorimetric assay and a high-performance anion-exchange chromatography with a pulsed electrochemical detector for product analysis, it was shown that the endoglucanase hydrolysed exclusively linear 1,3-beta-glucan chains, had an optimum pH of 7.

Attenuated virulence of uridine-uracil auxotrophs of Aspergillus fumigatus.

Aspergillus fumigatus mutants that are deficient in the de novo UMP biosynthesis pathway because of a mutation in the pyrG gene encoding orotidine-5'-phosphate decarboxylase (and therefore auxotrophic for uridine or uracil) were evaluated in a murine model of invasive aspergillosis. These mutants were entirely nonpathogenic, and mutant conidia remained ungerminated in alveolar macrophages. Both the germination and virulence defects could be restored by supplementing the drinking water of the animals with uridine.

Chemical and immunological characterization of the extracellular galactomannan of Aspergillus fumigatus.

The galactomannan (GM) produced extracellularly by Aspergillus fumigatus has been purified by a double sequential hydrazine-nitrous acid treatment of the ethanol precipitate of the culture filtrate. Nuclear magnetic resonance and gas-liquid chromatography-mass spectrometry analysis have been performed on intact GM, acid-hydrolyzed GM, and oligomers resulting from the acetolysis of the acid-hydrolyzed GM. Results show that A.

[Tools, progress and questions in the molecular study of Aspergillus fumigatus and invasive aspergillosis].

Development of A. fumigatus in the host tissues is due to the intrinsic biological characteristics of this fungus and to the impairment of the cellular defence reactions of the host. However, even today the understanding of the factors governing the infectivity of A.

Aspergillus fumigatus metalloproteinase that hydrolyses native collagen: purification by dye-binding chromatography.

A proteinase was purified from the human pathogenic fungus Aspergillus fumigatus. The four chromatographic steps, a "negative" dye column, a "positive" dye column, hydroxyapatite Ultrogel, and modified TSK gel (HW 55), gave a 14% overall yield. The protein migrated as a single band on SDS-PAGE and isoelectric focusing, with an M(r) of 82,000 and a pI of 5.

Characterization of the 1,3-beta-glucan synthase of Aspergillus fumigatus.

1,3-beta-Glucan synthase activity has been detected in a membrane fraction extracted from the mycelium of the filamentous fungus Aspergillus fumigatus. The enzyme was solubilized by CHAPS and stabilized by filtration on a Bio-gel P30 column. Highest activity was obtained in the early exponential phase of growth.

A transformant of Aspergillus fumigatus deficient in the antigenic cytotoxin ASPFI.

The aspfI gene encoding a ribonucleotoxin, a putative virulence factor of Aspergillus fumigatus, was inactivated by gene disruption. Gene replacement through homologous recombination by the disrupted allele tagged by the hygromycin B resistance marker was performed by transformation of a pathogenic strain. One transformant with the disrupted aspfI gene failed to produce the ASPFI protein and was shown to be pathogenic for mice.

Cell wall antigens in Aspergillus fumigatus.

The Aspergillus cell wall contains most of the antigens secreted by the fungus during its active in vitro or in vivo growth. These antigens, which bind to the IgE and IgG of allergic and aspergilloma patients or are secreted in the biological fluids of patients with invasive aspergillosis, are of primary importance in the diagnosis of aspergillosis. Located at the interface between host and pathogen cells, the fungal cell wall plays a major role during fungal invasion.

Ultrastructure and composition of the conidial wall of Cladosporium cladosporioides.

Transmission electron microscopy revealed that the conidial wall of Cladosporium cladosporioides was constituted of an electron-lucent inner layer and an electron-dense outer layer. The conidial surface is covered by rodlet fascicles which can be removed by ultrasonication. Ultrastructurally, the 100,000 X g ultracentrifugation pellet of the ultrasonicated extract containing the rodlet layer appeared as an amorphous structure containing probably internal wall material anchoring the rodlet fascicles on the wall.

[A new culture medium for growth and sporulation of Entomophthorales species, pathogens of aphids (author's transl)].

No one of the 3 specific egg yolk fractions (neutral lipids, polar lipids and proteins) was necessary for growth and sporulation of species such as Entomophthora aphidis, E. phalloides and E. thaxteriana, normally grown on egg yolk media.