Question

If performed correctly, the streak plate technique results in the dilution of the culture and the formation of isolated colonies from individual cells. Explain how the technique achieves this.

Answer 1

Streak plate is a pure culture technique. It is used to isolate a pure culture from a mixed population. The culture is "streaked" on a solid medium, which eventually thins out and forms individual colonies.
The principle is that while streaking put, the inoculum is diluted to a point where one cell is inoculated.

Region 1 is where streaking out begins. Hugh and dense population of bacteria is seen here. The plate is rotated $\fn_jvn 90^{\circ}$ , and the streaking is continued. Here, heavy growth is observed. The steps is repeated, until you reach back to region 1. No inoculum is taking in-between. The inoculum is diluted with each streak. The last round of streaking will have a diluted population of bacteria and thus, individual, well-separated colonies will be formed that can be isolated and cultured again.

Start here Heavy confluent growth Individual colonies 4 2 Heavy growth 3 Light growth