WEEK 2 BIO2071 MICROBIOLOGY 2071

Review Sheet

Based on your knowledge from the lab manual readings from this week, create a 2- to 3-page document in Microsoft Word for providing answers to questions in the following review sheets:

• Week 2 Review Sheet

Submission Details

• Support your responses with examples.


• Cite any sources in APA format.


• Name your document SU_BIO2071_W2_A2_LastName_FirstInitial.doc.


• Submit your document to the Submissions Area by the due date assigned   Week 2 – Review Sheet Exercise 4: Pure bacterial colonies 1. 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 may be 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 cultures 1. Discuss the relative convenience of pour- and streak-plate techniques in culturing clinical specimens. 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 of extraneous contamination? Exercise 3: Primary media for isolation of microorganisms 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. What is the major difference between Modified Thayer-Martin (MTM) and chocolate agar? When would you use MTM rather than chocolate ag