Posted: April 28th, 2017

Distinguish between a pure culture and a mixed culture.


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 agar?


Expert paper writers are just a few clicks away

Place an order in 3 easy steps. Takes less than 5 mins.

Calculate the price of your order

You will get a personal manager and a discount.
We'll send you the first draft for approval by at
Total price:
Live Chat+1-631-333-0101EmailWhatsApp