Distribution and conformation of crystalline nigeran in hyphal walls of Aspergillus niger and Aspergillus awamori

Abstract

Hyphal walls ofAspergillus awamori containing increased amounts of the aglucan, nigeran, became correspondingly more opaque when viewed in the electron microscope as shadowed preparations. However, increased polymer deposition was not accompanied by any significant change in wall thickness. The nigeran of both A. awamori and Aspergillus niger occurred in situ in a crystalline conformation identical to that of single crystals prepared with pure polysaccharide. Furthermore, this polymer was the dominant crystalline material in the hyphae whether or not they were enriched in nigeran. Enzymic digestion of nigeran in A. niger and A. awamori revealed that the bulk of the polymer was exposed to the cell's exterior. However, a certain fraction was accessible to enzymic attack only after the wall was treated with boiling water. A third portion, detectable only by X-ray diffraction, was associated with other components and could not be extracted, even with prolonged boiling. It was removed by hot, dilute alkali and was associated in the wall with another glucan fraction. Dry heating of A. niger walls altered their susceptibility to enzymic digestion of nigeran in situ. It is proposed that this treatment introduces interstices in the crystal surface that facilitate attack. MATERIALS AND METHODS Growth of organism. A. awamori Nakazawa QM 873 (A. luchuensis3 was grown from spores aerobically in submerged cultures at room temperature (22 to 23°C) in a complete medium consisting of (per liter of deionized water): sucrose (30.0 g), NH4NOQ (1.0 g), MgSO4 7H20 (0.3 g), KH2PO4 (1.26 g), yeast 691

Production and composition of an exocellular Nigeran-protein complex isolated from cultures of Aspergillus awamori

“…Nigeran, a linear a-D-glucan with alternating (1--3) and (1)(2)(3)(4) linkages, is a highly crystalline matrix component of certain Aspergillus and Penicillium species (8,33). Deposition is primarily on the exterior surfaces of the hyphal walls and occurs as the nutritional sources are depleted of available nitrogen (8,18).…”

“…Nigeran, a linear a-D-glucan with alternating (1--3) and (1)(2)(3)(4) linkages, is a highly crystalline matrix component of certain Aspergillus and Penicillium species (8,33). Deposition is primarily on the exterior surfaces of the hyphal walls and occurs as the nutritional sources are depleted of available nitrogen (8,18). The lamellarchain-folding character of nigeran renders it and the balance of the hyphal wall resistant to enzymatic attack (8,23) and lysis (18), suggesting a protective function.…”

“…Deposition is primarily on the exterior surfaces of the hyphal walls and occurs as the nutritional sources are depleted of available nitrogen (8,18). The lamellarchain-folding character of nigeran renders it and the balance of the hyphal wall resistant to enzymatic attack (8,23) and lysis (18), suggesting a protective function.…”

El exómero de Schizosaccharomyces pombe colabora en el tráfico vesicular entre el aparato de Golgi y el sistema endosomal

“…pombe (18-28% del total) como en la de otros hongos dimórficos y filamentosos (Bush et al, 1974;Bobbitt et al, 1977); sin embargo, está ausente en la pared celular de S.…”

Papel de los reguladores de Rho-GTPasas, Rgf1p y Rgf2p, en el control de la integridad y la polaridad en Schizosaccharomyces pombe

“…El α-glucano está presente en la pared celular de S. pombe y otros hongos dimórficos y filamentosos, como Histoplasma capsulatum, Paracoccidioides brasiliensis y Blastomyces dermatitidis, aunque curiosamente se encuentra ausente en la pared celular de S. cerevisiae (Bobbit et al, 1977;Bush et al, 1974;Hogan and Klein, 1994;Klimpel and Goldman, 1988;San-Blas et al, 1977).…”