14. You have isolated a strain of bacteria S1 that causes infections. You would

Question

14. You have isolated a strain of bacteria S1 that causes infections. You would like to find phages that kill bacteria from strain S1, but that do not affect another benign strairn S2 that is normally found in the human gut. You have a solution of purified phages (obtained from wastewater) that contains a mixture of different phage types, some of which you expect to be able to lyse S1 but not S2. Which procedure could you follow to isolate the type of phage that you could use to cure infections by S1 while preserving S2? A: Prepare plates with a lawn of bacteria S1, apply a diluted phage solution, retrieve phage from each plaque that is formed, for each phage apply it to a population of S2 bacteria, and keep phages that can replicate on S2. B: Prepare plates with a lawn of bacteria S1, apply a diluted phage solution, retrieve phage from each plaque that is formed, for each phage apply it to a population of S2 bacteria, and keep phages that cannot lyse S2. C: Prepare plates with a lawn of bacteria S2, apply a diluted phage solution, retrieve phage from each plaque that is formed, for each phage apply it to a population of S1 bacteria, and keep phages that can lyse S1 D: Prepare plates with a lawn of bacteria S2, apply a diluted phage solution, retrieve phage from each plaque that is formed, for each phage apply it to a population of S1 bacteria, and keep phages that cannot lyse S1

Explanation / Answer

Right answer- B. Prepare plates with a lawn of becteria S1,aplly a diluted phage solution, retrieve phage from each plaque that is formed, for each phage apply into a population of S2 bacteria and keep phages that cannot lyse S2.

Explanation- we always use the bacteria in same as infection by higher dilution factors ( as per concept by antibiotics) or we can use that same bacteria by removing pathogenic property ( as per concept of vaccines and toxoids).

that means we must be use the same plate as S1 that will effective against the S1. It will not lyse the S2 bacause it has another nature in living and celluler functioning.

explanation for A- It is prepare by the S1 but our target is to prevent from lyse of S2 not to improve replication.

Explanation for C- the plates is prepared by S2 means it may not be effected to S1.

Explanatio D- same as per C it is prepare by S2 so it may not be affected on infection caused by S1

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