1. Which approach or approaches would you use to isolate and then purify microbi

Question

1.  Which approach or approaches would you use to isolate and then purify microbial cells from a natural environmental sample?

a) Streak plate and then Spread plate

b) Spread plate and then Streak plate

c) Streak plate only

d) Spread plate only

e) Spread plate and Gram strain

2.  During streak plate inoculation, what is the purpose of flaming the inoculation loop between each set of streaks across an agar plate? (eg. see Figure 1 in the schedule)

a) So that microbial numbers on the loop increase after flaming after each set of streaks is conducted

b)So that microbial numbers on the loop decrease after each set of streaks is conducted

c) So that single colonies will ultimately be produced on the plate

d)  Answers a and c are correct

e) Answers b and c are correct

Explanation / Answer

1. You can use a streak plate and then spread plate. Streak plate is used to isolate discrete colonies. It is basically a dilution technique where you start with a loopful of a mixed population of bacteria and it gets diluted out when you keep on streaking it and ultimately you will get pure culture and single colonies of the bacteria. From these single colonies, you can put cultures and do the spread plating to look at the morphology of colonies and do some biochemical tests to identify the microorganisms.

2. The loop is flamed so that microbial numbers on the loops decreases after each set of the streaks is conducted and ultimately single colonies are produced.

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