Streaking Method

One drop of bacteria solution contains millions of cells. To identify a species, individual strains have to be grown separately—starting from a single cell. The most commonly used method to isolate a single cell is called the streaking technique. There are several different methods to streak a plate.

These methods all follow the same basic principle: a large number of cells are spread over the surface of an agar plate until they are far enough apart from each other.

Have a look at the different streaking patterns bellow and try them out in the virtual lab. The numbers and colors refer to the order of the streaks. E.g. streak number two is started with a sterile loop inside streak number one to pick up bacteria.

The plate is then incubated and the cells start to divide and form colonies. Single cells form colonies of genetically identical clones. An isolated colony usually grows bigger due to less competition for nutrients.