Yeast is everywhere, on plants, on fruit, in the air…and in beer. Streaking an agar plate is a quick and easy way to isolate yeast, to check for purity, and to re-culture yeast from sources like a bottle-conditioned beer or your own fermenter. A sterile inoculation loop is dipped into a sample of yeast and streaked over the agar surface on a plate in a pattern of decreasing cells. The last cells to rub off the loop are wide-enough apart so that they grow into isolated colonies. It’s easier than it sounds and Brew Your Own Magazine’s Technical Editor Ashton Lewis walks you through how to streak a yeast source on an agar plate to isolate colonies to possibly use in your next batch of beer.