STUDIES ON THE AEROBIC OXIDATION OF FATTY ACIDS BY BACTERIA II

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Abstract
Glucose-grown cells of S. marcescens oxidized all straight-chain saturated fatty acids from acetic through myristic with an appreciable lag period with the exceptions of propionic, butyric, and valeric, which were not oxidized at all. Cells grown on a medium containing one of the fatty acids as the sole source of carbon or cells allowed to oxidize a small amt. of one of the fatty acids showed no lag period or a greatly reduced lag period in the oxidation of the homologous acid as well as in the oxidation of all the other fatty acids. Alpha-beta unsaturated, beta-hydroxy, and beta-ketocapric acid were also oxidized after a considerable lag by glucose-grown S. marcescens cells. Growth on caprate eliminated the lag period in the oxidation of the caprate derivatives. Exposure to any of the caprate derivatives eliminated or greatly reduced the lag periods in the oxidation of the other caprate derivatives and caprate, caprylate, and undecylate. Several possible explanations for the observed lag periods and their elimination are discussed. It is postulated that a single enzyme system, in which the individual enzymes function in a repeating sequence, catalyze the degradation of all the fatty acids oxidized by S. marcescens (acetic acid excluded). The data are consistent with either multiple alternate oxidation or a somewhat modified form of beta oxidation; no choice between the 2 mechanisms is possible as yet.