E. coli K-12 MG1655 was obtained from the E. coli Genetic Stock Center (New Haven, CT) and was the background strain used in this work. Strain RL01 was constructed by deleting the fadD gene from the MG1655 chromosome by λRed-mediated recombination (Datsenko and Wanner, 2000) using the λRed recombinase encoded on plasmid pKD46.