Figure 1.

Peroxisome multiplication imaged. Hansenula polymorpha cells are shifted from glucose- to methanol media, conditions that require peroxisome functions for growth. On glucose, characteristically a single peroxisome is present per cell (A) that—upon a shift to methanol containing media—incorporates alcohol oxidase (C), catalase and dihydroxyacetone synthase proteins, which are essential for growth on methanol. As a result the organelle increase in size (B) and, after maturation, forms a new organelle by fission (D) that subsequently will grow. A similar a-symmetric fission machinery is responsible for the administration of small organelles to the yeast bud (E). When the culture has reached the late exponential phase of growth, typically 4–6 organelles are present of comparable shape. The cuboid shape is due to the presence of large luminal alcohol oxidase crystals. M, mitochondria; N, nucleus; P, peroxisome. Cells are fixed with KMnO4, except (C,F), which are glutaraldehyde fixed. In these cells alcohol oxidase activity is demonstrated using CeCl3.