please answer all the questions : 1. Application question: Why is succinate impo
ID: 205432 • Letter: P
Question
please answer all the questions :
1. Application question: Why is succinate important when explaining that E. coli evolved to take up citrate under
conditions with oxygen?
2.Fully describe the E. coli cit operon as it functions in conditions without oxygen. Include promoter, repressor and
operator in your description.
3. How did this new arrangement facilitate the transcription of the citT primary transcript under conditions without oxygen?
How did this new arrangement facilitate the transcription of the citT primary transcript under conditions with oxygen?
4. Synthesis question: Explain the advantages and disadvantages of the citrate operon mutation in E. coli living in a flask with E. coli that do not have this mutation.
Explanation / Answer
1) The mutant E. coli was able to grow under aerobic condition showing that citT genes was transcribed and citrate was utilized by bacteria in the presence of oxygen. citT expression resulted in the accumulation of succinate outside the bacterial cell showing that besides glucose and citrate, succinate can also be utilized by the mutant strain.
2) cit or citrate operon is a negative controlled repressible operon as bacteria cannot utilise citrate in the presence of oxygen, i.e., cit operon get repressed in the presence of oxygen. It consists of a promoter that transcribes the structural genes only under anaerobic condition. One of the structural gene, citT, that encodes translocator is responsible for the transport of citrate into the cell in the exchange of succinate, acting as a antiporter.
In the presence of oxygen, repressor is activated and binds to the operator and hence inhibit the expression of citT gene, that inturn inhibits the import of citrate in the cell. Citrate functions as an energy source because it produces 2ATP and 2 NADH.
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