Effects of lipids, fatty acids, and other detergents on bacterial utilization of hexadecane

Fatty acids, lipids, and detergents affected hexadecane utilization by Acinetobaeter lwoffi and Pseudomonas aeruginosa. Long-chain fatty acids (palmitic, oleic, and stearic) stimulated hexadecane utilization, as did triglycerides (tripalmitin, trioctanoin, trilaurin, and olive oil), lecithin, lysolecithin, hexadecanol, and wax esters (palmityl palmitate and palmityl stearate). Hexadecane in turn stimulated the utilization of tripalmitin for growth by A. lwoffi. Propionic acid caused diauxic growth, apparently being utilized before hexadecane. Isobutyric acid was not used for growth and inhibited hexadecane utilization. Caprylic and lauric acids, octan-2-ol, and phenethyl alcohol inhibited hexadecane utilization. The detergents Triton X-100, Brij 35, and FL-70 were not themselves used for growth, but stimulated growth on hexadecane.In A. lwoffi, palmitic acid suppressed diauxic growth on a mixture of ethanol and hexadecane if added while ethanol was being oxidized, but not if added subsequently. Lecithin also suppressed diauxic growth, but Triton X-100 did not, though it shortened the lag period before hexadecane utilization.Washed suspensions of cells grown on ethanol or hexadecane could not oxidize hexadecane unless Triton X-100 was also added. Then hexadecane-grown cells oxidized hexadecane about 3 times as fast as ethanol-grown cells. The results suggest that fatty acids and other lipids stimulate growth on hexadecane partly, but not solely, by acting as emulsifying agents. They may also act as inducers of enzymes necessary for hexadecane breakdown, or they may be incorporated into cell membranes and change their properties so that hexadecane can more readily enter the cells.