South University Pure Bacterial Colonies Pour Plate and Streak Plates Questions

When an agar plate is inoculated, why is the loop sterilized after the initial inoculum is put on?

Distinguish between a pure culture and a mixed culture.

1. Define a bacterial colony. List four characteristics by which bacterial colonies may be distinguished.
2. Why should a Petri dish not be left open for any extended period?
3. Why does the streaking method you used to inoculate your plates result in isolated colonies?
4. Exercise 5: Pour plate and streaking technique to obtain pure cultures
5. Discuss the relative convenience of pour- and streak-plate techniques in culturing clinical specimens.

How do you decide which colonies should be picked from a plate culture of a mixed flora?

Why is it necessary to make pure subcultures of organisms grown from clinical specimens?

1. What kinds of clinical specimens may yield a mixed flora in bacterial cultures?
2. When more than one colony type appears in pure culture, what are the most likely sources of extraneous contamination?
3. Exercise 3: Primary media for isolation of microorganisms
4. 1. Define a differential medium and discuss its purpose.
   2. Define a selective medium and describe its uses.
   3. Why is MacConkey agar selective as well as differential? 4. Why is blood agar useful as a primary isolation medium?
5. 5. What is the major difference between Modified Thayer-Martin (MTM) and chocolate agar? When would you use MTM rather than chocolate agar?