The aldB gene, which codes for a functional aldehyde dehydrogenase is induced by ethanol, a VOC that exists in higher concentrations in the breath of lung cancer patients. In E. Coli, the metabolism of ethanol consists of its transformation into an aldehyde and then into a carboxylic acid. The latter product then reacts with the g protein receptor, thus triggering a series of reactions that eventually effects the Crp-cAMP complex, a dual regulator complex that regulates the expression of the DNA sequence. cAMP binds to Crp, thus changing the form of Crp, and this newly conformed Crp attaches to the promoter, increasing the affinity of the DNA sequence to RNA Polymerase. Crp is also known as CAP, which stands for catabolite activator protein and is present in E. Coli under normal conditions. After RNA Polymerase binds to the promoter and then initiates transcription. By placing GFP after the aldB coding sequence, we will ensure that GFP is also expressed and thus, in the presence of ethanol, the bacteria will glow.
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