In a microbial culture experiment, it is expected that there are 5 x 106 (5 mill

Question

In a microbial culture experiment, it is expected that there are 5 x 106 (5 million) culturable bacteria in each millilitre of seawater. Following the generation of a tenfold dilution series from 10-1 to 10-5, 100 1 of liquid from each tube was pipetted and spread onto separate agar plates. From which dilution tube would you expect to have a plate containing 50 colonies? 2. a) 101 dilution b) 102 dilution c 0- dilution d) 104dilution e 10- dilution 3. 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 4. During streak plate inoculation, when heat sterilizing an inoculation loop, why do you touch the loop onto the surface of the plate before touching the loop onto the colony which you wish to sub-culture? a) So that you kill the microbial cell prior to sub-culture b) So that you do not kill the microbial cell prior to sub-culture c) So that you transfer nutrients in the agar onto the inoculation loop during sub-culture, so the microbial cell does not die whilst on the loop d) Answers a and c are both correct e) Answers b and c are both correct

Explanation / Answer

2)-option e is correct because in first dilution tube the number of colonies are larger and in last tube the number is less.

3)-optipn c is correct because streaking technique used to isolate microbes.

4)- option b is correct because when microbes comes in contact of heat then they are killed.

5)-option c is correct because after flaming some microbes are killed and in last we get single colony.

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