Yeast Mitochondria

 
There's a paper in this month's issue of Developmental Cell that uses the technique of electron tomography to examine the fine structure of a yeast cell. This technique involves slicing the cell into many thin sections then taking electron micrographs of each section and reconstructing a three-dimensional model of the cell.

The species is the fission yeast Schizosaccharomyces pombe and the results are spectacular. The image on the left was part of the Bio News Net press release.

The emphasis in the paper is on the organization of microtubules. Those are the thin green lines runing down the length of the cell. It turns out that many of the vesicles and mitochondria are associated with these microtubules. Here's the abstract of the paper ..

Polarized cells, such as neuronal, epithelial, and fungal cells, all display a specialized organization of their microtubules (MTs). The interphase MT cytoskeleton of the rod-shaped fission yeast, Schizosaccharomyces pombe, has been extensively described by fluorescence microscopy. Here, we describe a large-scale, electron tomography investigation of S. pombe, including a 3D reconstruction of a complete eukaryotic cell volume at sufficient resolution to show both how many MTs there are in a bundle and their detailed architecture. Most cytoplasmic MTs are open at one end and capped at the other, providing evidence about their polarity. Electron-dense bridges between the MTs themselves and between MTs and the nuclear envelope were frequently observed. Finally, we have investigated structure/function relationships between MTs and both mitochondria and vesicles. Our analysis shows that electron tomography of well-preserved cells is ideally suited for describing fine ultrastructural details that were not visible with previous techniques.

One of the most interesting things about this paper is that it illustrates the structure of mitochondria. Look at the picture on the right from their paper. The gold things are mitochondria and they appear to be stuck to microtubules. Individual mitochondria are shown in the inserts in order to illustrate the convoluted and branching structures of those that are associated with microtubules. (The one labelled "G" is not stuck to microtubules.)

Most people don't realize that mitochondria are so complicated. Furthermore, the structures are dynamic—they can change significantly in the space of minutes.

Höög, J.L., Schwartz, C., Noon, A.T., O'Toole, E.T., Mastronarde, D.N., McIntosh, J.R., and Antony, C. (2007) Organization of Interphase Microtubules in Fission Yeast Analyzed by Electron Tomography. Developmental Cell 12: 349-361.