Chloe Evetts (8990-4674)
May 15, 2013
Isolation of Colonies from a Mixed Culture (Streak-Plate Technique)
The purpose of this experiment is to learn how to isolate a culture by streaking.
Being able to isolate a single organism is an extremely important aspect to
working in a microbiology lab. In order to examine a specific organism on a petri
dish, that organism must be isolated from the many other types of organisms that
may be present. To do so, the aseptic technique, as well as properly streaking a
petri dish must be employed. The goal of this experiment is to isolate an E. coli
organism by transferring it from one petri dish to another.
Although there are many microbes present, by using the aseptic technique and
the streaking method, a single organism should be able to be isolated so that it
can be studied independently of the rest of the organisms within one petri dish.
1. Label the bottom of the BHA petri dish with your name, date, petri dish
media and test microorganism (in this case, E. coli).
2. Engage Bunsen burner by turning on the gas, and using the striker.
3. Hold inoculating loop over flame until it turns red. It is now sterile.
4. Scrape up some of the sample (E. coli) with the inoculating loop.
5. Begin the streaking procedure as shown below in the diagram.
6. After the loop is lifted each time, place over the