Transport of long-chain fatty acids by Escherichia coli: mapping and characterization of mutants in the fadL gene.

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Abstract
A new locus (fadL) that is required for the utilization of long-chain fatty acids was mapped and partially characterized in an E. coli mutant. The fadL locus was mapped at 50 min on the chromosome. A mutant bearing a defect in this locus cannot utilize long-chain fatty acids as a sole C source. Derivatives of this mutant that can grown on decanoate (termed fadR) are capable of growth on medium-chain but not long-chain fatty acids. The fadL mutant is apparently defective in the transport of long-chain fatty acids into the cell for the following reasons: fadR fadL strains can oxidize in vivo decanoate but not oleate; neither fadL nor fadR fadL strains can incorporate oleate into their membrane lipids; the activity of the acyl-CoA synthetase (EC 6.2.1.3) in fadR fadL strains is comparable to the acyl-CoA synthetase activity in fadR fadL+ strains; and in vitro extracts from fadR fadL strains can oxidize oleate at rates comparable to those from fadR fadL+ strains. If the above hypothesis is correct, the uptake of long-chain fatty acids by E. coli requires at least 2 gene products.