Identifying bacteria and smaller yeast in a brewery sample can be difficult using wet mounts and conventional widefield microscope illumination. Visualizing these smaller organisms, and identifying intracellular structures in yeast, requires a more robust and specialized approach to imaging. Specifically, it requires the staining of dried samples with dyes that emphasize cell shape and structure.
This approach is required if you wish to track the presence of bacteria during mixed ferments, or identify the presence of smaller yeasts and bacteria in your brewery samples. In this video I demonstrate the dry mount technique, which is the first step in a range of staining approaches. I then demonstrate the use of three simple and inexpensive stains – safranin o, trypan blue and malachite green – to stain yeast and bacteria on dry mounts.
The stains demonstrated in this video are merely an introduction to the vast array of staining approaches that can be applied to dry mounts. While not covered in this video, more advanced staining methods can be applied to dry mounts, allowing for improved identification of bacteria in your samples (e.g. Gram staining) or identification of specific cellular structures (e.g. India ink to identify bacteria with capsules).