In: Biology
How would you design a regulatory system to make Escherichia coli use succinic acid in preference to glucose? How could you modify it so that E. coli prefers to use succinic acid in the light but glucose in the dark?
For devising a regulatory system in E.coli which utilises succinc acid in preference to glucose in the presence of light and in absence of light utilise glucose, can be done by using the suitable promoter, operator and inducer proteins and the subsequent enzymes that utilise succinct acid in the Krebs cycle. For the regulatory region of the operon, we can add the photosystem II genes which get activated in the presence of light thereby activating the promoter regions and in the absence of light PSII genes would be inactive thereby inactivating the promoter regions. For the glucose to be utilised when succinct acid is absent, the cAMP-CRP complex regulatory gene can be incorporated. This gene acts as the operator 2 gene which in the presence of glucose, low cAMP levels will be there and the cAMP-CRP complex will be inactive and the promoter will be inactive and when glucose is absent, cAMP levels will be high and the complex will get activated which will thereby activate the promoter region. The inducer should be such that the succinc acid presence should activate the promoter and the absence should stop or inactivate the operon. This is the regulatory region explained so far. For the structural genes, the enzymes encoding succinic acid dehydrogenase, fumarase and malate dehydrogenase can be incorporated in the structural genes.
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