Regulation of fatty acid biosynthesis in the hydrocarbon oxidizing microorganism, Acinetobacter sp.

Abstract

1. The regulation of fatty acid biosynthesis was studied inAcinetobacter strainHOl-N, a microorganism which grows on long chain paraffinic hydrocarbons. Dual-label experiments with acetate-3H and palmitate-1-14C were designed to assess the differences in fatty acid metabolism between hexadecane-and acetategrown cells: 2. Experiments involving non-growing conditions indicated a preferential labeling of the cellular lipids with acetate-3H in acetate-grown cells and palmitate-1-14C in hexadecane grown cells. In addition to this relationship, non-growing cells assimilated exogenous lipid precursors (acetate) or preformed lipid (palmitate) almost exclusively into the cellular neutral lipids. 3. Under growing conditions acetate-grown cells exhibited a transfer of lipid radioactivity from the neutral lipid fraction to the phospholipid fraction. 4. Hexadecane-grown cells preferentially labeled with palmitate-1-14C in the cellular lipid exhibited a 98–100% loss of neutral lipid radioactivity. 5. Palmitate derived directly from hexadecane oxidation diluted the radioactive free fatty acid pool 4 times faster in hexadecane-grown cells than in acetate-grown cells. 6. These results indicate that cells grown at the expense of hexadecane are characterized by mechanisms more efficient in the transport and assimilation of exogenous fatty acid and thatde novo fatty acid biosynthesis is significantly reduced in hexadecane-grown cells.