Fig. 1. Intracellular mitochondrial networks. (A) Branched mitochondrial network in a budding yeast cell. A yeast strain expressing mitochondria-targeted green fluorescent protein was grown on the non-fermentable carbon source glycerol to logarithmic growth phase. The cell wall was stained with calcofluor white. A surface-rendered three-dimensional stack recorded with an MMM-4Pi confocal fluorescence microscope is shown. The length of each arrow corresponds to 1 µm. Reproduced from Egner et al. (2002) with permission. © 2002 National Academy of Sciences, USA. (B) Extended and interconnected mitochondrial filaments in a COS-7 cell (african green monkey fibroblast). Mitochondria were stained by indirect immunofluorescence against cytochrome c. The image was kindly provided by Ansgar Santel, Stanford University, CA.