Ultrastructural modifications of the cell wall and cell interior of micafungin-treated hyphae were revealed by TEM. Major changes are the disorder of septum formation, and accumulation of electron-dense inclusions in the cell wall and in the space between the cell membrane and the cell wall. Figure 7 shows a typical feature of hyphae with incompletely or aberrantly formed septa, leading to dispro- portionate segmentation of hyphae, which were seen in cultures treated with 0.1 mg ml—1 micafungin for 5 h.