Subapical wall synthesis and wall thickening induced by cycloheximide in hyphae of Aspergillus nidulans.

Hyphae of Aspergillus nidulans continued to synthesize all the major polysaccharide components of the cell wall when cycloheximide was added to cultures. In the presence of cycloheximide, hyphae did not elongate, but electron microscopy showed that the walls became thicker around the cell. The conclusion that cycloheximide changed wall synthesis from extension at the apex to subapical thickening was supported by grain distributions on radioautograms of mutant hyphae labeled with galactose. These findings are discussed in relation to the control of hyphal wall synthesis and are compared with the effects of protein synthesis inhibitors on wall formation in gram-positive bacteria.