Week 2 – Review SheetExercise 4: Pure bacterial colonies1. When an agar plate is

Week 2 – Review SheetExercise 4: Pure bacterial colonies1. When an agar plate is inoculated, why is the loop sterilized after the initial inoculum is put on?2. Distinguish between a pure culture and a mixed culture.3. Define a bacterial colony. List four characteristics by which bacterial colonies maybe distinguished.4. Why should a Petri dish not be left open for any extended period?5. Why does the streaking method you used to inoculate your plates result in isolated colonies?Exercise 5: Pour plate and streaking technique to obtain pure cultures1. Discuss the relative convenience of pour- and streak-plate techniques in culturing clinicalspecimens.2. How do you decide which colonies should be picked from a plate culture of a mixed flora?3. Why is it necessary to make pure subcultures of organisms grown from clinical specimens?4. What kinds of clinical specimens may yield a mixed flora in bacterial cultures?5. When more than one colony type appears in pure culture, what are the most likely sources ofextraneous contamination?Exercise 3: Primary media for isolation of microorganisms1. 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. What is the major difference between Modified Thayer-Martin (MTM) and chocolate agar? Whenwould you use MTM rather than chocolate agar