Summary
A method for embedding yeast colonies allowing sectioning for light and electron microscopy. This protocol allows determination of the distribution of sporulated cells and pseudohyphal cells within colonies providing a new tool toward understanding the organization of cell types within a fungal community.
Abstract
Patterning of different cell types in embryos is a key mechanism in metazoan development. Communities of microorganisms, such as colonies and biofilms also display patterns of cell types. For example, in the yeast S. cerevisiae, sporulated cells and pseudohyphal cells are not uniformly distributed in colonies. The functional importance of patterning and the molecular mechanisms that underlie these patterns are still poorly understood.
One challenge with respect to investigating patterns of cell types in fungal colonies is that unlike metazoan tissue, cells in colonies are relatively weakly attached to one another. In particular, fungal colonies do not contain the same extensive level of extracellular matrix found in most tissues . Here we report on a method for embedding and sectioning yeast colonies that reveals the interior patterns of cell types in these colonies. The method can be used to prepare thick sections (0.5 μ) useful for light microscopy and thin sections (0.1 μ) suitable for transmission electron microscopy. Asci and pseudohyphal cells can easily be distinguished from ovoid yeast cells by light microscopy , while the interior structure of these cells can be visualized by EM.
The method is based on surrounding colonies with agar, infiltrating them with Spurr’s medium, and then sectioning. Colonies with a diameter in the range of 1-2 mm are suitable for this protocol. In addition to visualizing the interior of colonies, the method allows visualization of the region of the colony that invades the underlying agar.
Protocol
Discussion
The method presented reveals the interior structures of colonies. Because the method is effective in determining patterns of cell types in a range of S. cerevisiae strains with different colony morphologies, and also in a related species S. paradoxus 5, the method is also likely to work on a wide range of fungi and other microorganisms.
One critical step for the success of the method is to ensure that the entire colony, including the top of the colony, is encased in agar …
Declarações
The authors have nothing to disclose.
Acknowledgements
Research was funded by NIH 1R15GM094770.
Materials
| Material Name | Tipo | Company | Catalogue Number | Comment |
|---|---|---|---|---|
| Osmium tetroxide | Electron Microscopy Sciences | RT 19152 | ||
| Silicone embedding molds | Fisher Scientific | NC 9975029 | ||
| Cycloaliphatic epoxide resin | Electron Microscopy Sciences | RT 15004 | ERL 4221 | |
| Epoxy resin | Electron Microscopy Sciences | RT 13000 | DER 736 | |
| Nonenyl Succinic Anhydride | Electron Microscopy Sciences | RT 19050 | NSA | |
| 2-Dimethyl aminoethanol | Electron Microscopy Sciences | RT 13300 | DMAE | |
| Mounting media | KPL | 71-00-16 | ||
| Rotating wheel | Ted Pella | Pelco 1055 | ||
| Microtome | Leica | Ultracut S |
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