Transport in an Escherichia coli fatty acid auxotroph. A novel case of catabolite repression.

The transport of alpha-methylglucoside and a variety of amino acids including histidine, leucine, lysine, proline, and threonine are reduced 5- to 50-fold in Escherichia coli K1061, an unsaturated fatty acid auxotroph, when cells are grown in medium containing glucose as a carbon source and supplemented with either cis-vaccenic acid or cis-9, 10-methylenehexadecanoic acid. Cells grown in glucose medium containing oleate, palmitoleate, or cis-7-hexadecenoate do not exhibit this effect and transport alpha-methylglucoside and amino acids at rates comparable to those of a wild type strain. For cis-vaccenate- and cis-9, 10-methylenehexadecanoate-grown cells the capacity to transport amino acids and alpha-methylglucoside is normal when glycerol or succinate is the energy supply or when cyclic adenosine 3':5'-monophosphate is added to cultures growing on glucose. These results suggest that in this strain several transport systems are affected by catabolite repression, but the phenomenon is unique since repression requires not only glucose but specific unsaturated fatty acids, cis-vaccenic acid, or cis-9, 20-methylenehexadecanoic acid.