What is streaking
Streaking is a technique to spread culture over a substrate like agar in specific ways in order to create isolated colonies. There are many ways to streak culture and some are more tailored to specific goals.
The purpose of streaking is to extract yeast (or bacteria!) from a culture of many into colonies of few. In this case the magnitude of “few” means a few million. The idea is that we then have a better chance of isolating purified individual species. This allows us to more easily move them from these colonies elsewhere. Elsewhere could be further experimentation, growing, or storing for later.
Required materials
- Culture you’re interested in
- Agar plate
- Alcohol lamp
- Inoculation loop
There are a few different substitutions for inoculation loops. In particular sterilized tooth picks or needles can be used, the former only once, however.
Techniques
The basic technique is simple to state: you dip your sterilized loop into some culture and spread it across your dish in a methodical manner. But, there are some standard motions involved that are simply best seen. It is best to find a video on YouTube to see how it’s done as opposed to reading.
A few common techniques are full-plate, quadrant, and multi-culture.
Colonies
After your yeast streak plates have been growing for a few days you should see small white dots that look a bit like tiny drops of off-white paint. You should look for ones off by themselves. We expect that a culture growing off by itself it predominantly of the same species. You can then take samples of these with a sterilized inoculation loop and use them as needed.