Cell surface properties of Aspergillus fumigatus conidia: correlation between adherence, agglutination, and rearrangements of the cell wall

Abstract

Culture conditions that lead to swelling and germination dramatically influence cell surface characteristics and properties of Aspergillus fumigatus conidia. Conidial adherence to polystyrene and agglutination markedly increased during swelling, in a time-dependent manner. Agglutination appeared to be sensitive to cycloheximide and calcium. Removal of cell wall polysaccharides by lyticase or sodium metaperiodate suppressed agglutination of conidia. Proteinase K weakly decreased it whereas dithiothreitol strongly dispersed the cells. These observations suggest that both cell surface carbohydrates and proteins are involved in the agglutination process. Electron microscopic observations demonstrated that the cell wall of conidia was subject to some rearrangements during swelling, involving degradation and loss of the external convoluted layer, and subsequent exposure of underlying ligands. This was confirmed using lectins labelled with gold or fluorescein isothiocyanate, which showed that some carbohydrates, particularly those acting as ligands for peanut agglutinin, are largely exposed during the process. Finally, SDS-PAGE revealed major protein changes between resting and swollen conidia. We conclude that the ability of A. fumigatus conidia to aggregate correlates with an increase in adherence and biochemical reorganization of the cell wall.

Purification and Partial Characterization of a 32-Kilodalton Sialic Acid-Specific Lectin from Aspergillus fumigatus

“…A. fumigatus CBS 113.26 (Centraalbureau voor Schimmelcultures, Baarn, The Netherlands) was grown on yeast extractpeptone-dextrose agar at 37°C, and conidia were obtained from 5-day-old cul-tures by scraping the aerial mycelium in distilled water as described earlier (40). They were then pelleted by centrifugation (1,200 ϫ g, 3 min) and resuspended in distilled water, and the absorbance at 620 nm of the obtained suspension was adjusted to 0.6 (approximately 10 8 conidia/ml).…”

“…They were then pelleted by centrifugation (1,200 ϫ g, 3 min) and resuspended in distilled water, and the absorbance at 620 nm of the obtained suspension was adjusted to 0.6 (approximately 10 8 conidia/ml). Swollen conidia and germ tubes were obtained by inoculating 1.5 ml of the conidial suspension in petri dishes containing 15 ml of medium 199 (Sigma Laboratories) buffered at pH 7.6 as reported previously (40). After incubation at 37°C, the fungal elements were pelleted by centrifugation and resuspended in phosphate-buffered saline (PBS) (0.15 M, pH 7.2).…”

Innate Immunity toAspergillusSpecies

“…Conidial maturation triggers a profound morphological change that involves the loss of the proteinaceous hydrophobic layer and exposure of the inner cell wall (120,163). This cell wall is composed mainly of polysaccharides consisting of ␤-glucan, mannan, chitin, and galactomannan (89 (64,74,157), and optimal CD4 ϩ T-cell responses appear to occur only in response to live conidia (136).…”

Influence of mechanical stress and surface interaction on the aggregation of Aspergillus niger conidia

“…Filamentous fungi were classified into coagulating and non-coagulating types according to their ability to form aggregates. A large number of variables influencing fungal aggregation processes have been published (Amanullah et al, 2001;El-Enshasy et al, 1999;Fujita et al, 1994;Tronchin et al, 1995). Most studies dealing with this issue have drawn conclusions from the morphology of full-grown mycelia.…”