Structure and Composition of the Cell Wall of Neurospora crassa

Abstract

The structure and composition of the cell walls of hyphae of Neurospora crassa were investigated by electron microscopy, chemical analysis, and X-ray diffraction both before and after progressive enzymatic degradation by snail gut enzymes, chitinase, and trypsin. The wall consists of two phases: randomly disposed skeletal microfibrils of chitin only and an amorphous matrix which contains both #-glucans and protein. The protein contains a high percentage of the amides of aspartic and glutamic acid but no hydroxy-proline or cysteine. A portion of this protein is a component of or is associated with a system of pores which is embedded in the matrix of the wall. These pores, 40 to 70 A in outside diameter, sometimes branch and seem to provide a three-dimensional network from one side of the wall to the other. They may be a general system of transport across the walls.

Potassium Transport in Neurospora

“…This possibility is further supported by the finding that polymers of ethylene glycol and dextran with molecular weights up to 4700 pass readily through the Neurospora wall (46), as do secreted enzymes with much larger molecular weights (14,29,46). It is likely, then, that the cell wall is laced with waterfilled pores, and pores as large as 40 A in diameter have been tentatively identified in electron micrographs of the Neurospora wall (27). For these reasons, we have carried out the further analysis of K and Na fluxes at high pH assuming a parallel, rather than a series, arrangement of (fixed charge regions of) the cell wall and cytoplasm.…”

“…763 THE JOURNAL OF GENERAL PHYSIOLOGY · VOLUME 55 I1970 Energy Dependence The cell wall of Neurospora is composed mostly of neutral polysaccharides and does not contain the uronic acids common in higher plants. Work in several laboratories (25)(26)(27) has pointed to the presence of some negatively charged amino acids and phosphate residues within the wall, however, and it seemed possible that the fast component of flux might represent a stoichiometric exchange of newly added potassium ions for sodium which had been bound to the cell wall during the preincubation period. Considered simply, this case would require the fast component to be independent of metabolic energy, and therefore to be relatively insensitive to temperature changes and to metabolic inhibitors.…”

“…The cell wall of Neurospora is composed principally of neutral polysaccharides: chitin (poly-N-acetylglucosamine), /-glucan, and polygalactosamine (25)(26)(27). The two most likely sources of negatively charged sites within the Neurospora wall are relatively minor components, carboxyl residues of proteins and inorganic phosphate and polyphosphate groups, and information so far available on these compounds does not account quantitatively for the ion exchange data.…”

“…A second possibility is protein, which has been reported to constitute 12-15% by weight of the Neurospora wall (25,27). This protein fraction contains an unusually high proportion of acidic amino acid residues, aspartic and glutamic acids: 17.5% by weight of the total wall protein, or 21-26 mg for each gram of cell wall.…”

Effect of solvent concentration on the extraction kinetics and diffusivity of Cyclosporin A in the fungus Tolypocladium inflatum

“…The cell wall of N. crassa consists of an interconnected layered structure composed of an amorphous outer mixed aand b-glucan layer, a glycoprotein layer, a protein layer, and a chitinprotein microfibril layer (Gooday and Trinci, 1980;Hunsley and Burnett, 1970). The cell wall of N. crassa is approximately 0.1-0.3 mm thick with pores of 40-70 Å in diameter (Manocha and Colvin, 1967). The rate of mass transfer of CyA from the surface of the mycelia to the bulk liquid phase can be described by the following equation:…”