Molecular effect of FadD on the regulation and metabolism of fatty acid inEscherichia coli

Wild-type Escherichia coli can utilize exogenous long-chain fatty acids (C>12) as a sole carbon source for growth, but it cannot grow on medium-chain fatty acids. However, when the fadD gene from E. coli MG1655 was expressed in E. coli DH5alpha, the latter strain was found to utilize medium-chain fatty acids as its sole carbon source. Various E. coli strains thought to carry subtly different FadR phenotypes were all confirmed as using medium-chain fatty acids as their sole carbon source when the additional fadD was expressed. Semi-quantitative reverse transcription PCR analysis showed that the additional expression of fadD in E. coli strongly induced the expression of both fadE and fadBA. Excessive amounts of medium-chain acyl-CoA would probably bind to FadR and remove the inhibition of fatty acid beta-oxidation.