Abstract
Aspergillus niger and Penicillium urticae were shake-cultured, and the pellets formed were sectioned, stained and examined microscopically.
In general, the surface area of these mold pellets were found to be highly basophilic in comparison with the central area. A. niger was unable to form conidia in its pellets, whereas P. urticae formed conidia inside the surface area of the pellets. In this case the conidia were formed directly from hyphae without morphogenetic changes such as penicillus formation. In the central area of these pellets arthrospore-like cells resistant to staining were observed very frequently.
When A. niger pellets were treated briefly with 32P-phosphate, they Incorporated 32P actively. Autoradiography of the sections of these pellets showed that 32P was accumulated only on the surface of the pellets. When these pellets were further cultured for 1 day in a ‘cold’ medium, the dark ring in the autoradiogram remained unmoved and the outer area containing no 32P was formed by further growth of the hyphae. This suggests that in the growth process of the pellet there occurred no appreciable translocation of intracellular materials into newly formed hyphae.
Cytological features of the differentiation of pellet were compared with those of the surface colony which have been studied in detail in a previous work.
