Enzymatic degradation of the walls of spherules of Coccidioides immitis

The cell wall of the spherule phase of Coccidioides immitis was studied through the use of degradative enzymes and transmission electron microscopy. The evidence obtained indicated that the cell wall has multiple layers of differing chemical composition. In the mature cell wall, the inner half, adjacent to the cytoplasmic membrane, appeared to be a matrix of chitin and β-(1-3)-glucan. In contrast, the outer half of the cell wall was found to be largely α-(1-3)-glucan. Interspersed throughout the wall was what appeared to be a mannan-protein complex. This complex had the effect of masking the multiple layers of the wall, and appeared to be responsible for holding the layers together and anchoring the wall to the membrane. The evidence suggested a sequential addition of wall components to maturing cleavage planes of the endosporulating spherule.