1. Suppose you mix phage with bacteria in a 100 mL culture such that there is a
ID: 8516 • Letter: 1
Question
1. Suppose you mix phage with bacteria in a 100 mL culture such that there is a mean of 3 viable phage per mL. Now you add 1 mL of the culture to each of 20 soft agar tubes, pouring 20 plates with the soft agar/bacteria/phage mix. After overnight incubation the plaque count per plate results should be:A.3 plaques on every plate
B.A mean of 3 with plaques distributed according the Poisson distribution
C.No plaques on any plate
D.All plates would be completely lysed
Defend your answer.
2. Suppose you incubate bacteria overnight in each of 20 separate cultures. The next morning you mix phage with the bacteria in each culture such that there are many more phage per mL than bacteria. Now you add 1 mL of each culture to each of 20 soft agar tubes, pouring 20 plates with the soft agar/bacteria/phage mix. After overnight incubation the plaque count per plate results should be:
A.All plates would be completely lysed
B.plaques would appear on each plate distributed according to the Poisson distribution
C.No plaques would appear on any plate
D.Colonies would appear on plates distributed according to the Poisson distribution
Defend your answer.
Explanation / Answer
1. A As 1ml has 3 viable phages it means that each petriplate has 3 viruses. When viruses infect bacterial cells, they produce progeny. These progeny daughter cells infect the surrounding cells. We cannot view phages but we can see the lysis of the bacterial cells as plaques. As the progeny of each phage is around the mother virus there will be only 3 plaques seen. ----------------------------------------- 2 A As the concentration of phage is much more than the concentration of bacterial cells per ml of culture, it is most likely that the whole bacterial culture would be lysed. As the concentration of phage is much more than the concentration of bacterial cells per ml of culture, it is most likely that the whole bacterial culture would be lysed.Related Questions
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