Lipid Metabolism During Bacterial Growth, Sporulation, and Germination: Differential Synthesis of Individual Branched and Normal-Chain Fatty Acids During Spore Germination and Outgrowth of Bacillus thuringiensis
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The biosynthesis of individual branched- and normal-chain fatty acids during Bacillus thuringiensis spore germination and outgrowth was studied by comparing pulsed and continuous labeling of these fatty acids with [U- 14C ]acetate. The relative specific activity of each fatty acid varies with time as the cell progresses through outgrowth. However, fatty acid synthesis does occur in two distinct phases. Upon germination, acetate is incorporated only into the iso-isomers i-C13, i-C14, and i-C16; no normal or anteiso synthesis occurs. Subsequent to T30, the full complement of branched- and normal-chain homologues is formed and there is a dramatic enhancement in the overall rate of fatty acid synthesis. Significantly, this rate increase coincides with a marked shift from the synthesis of short-chain to long-chain fatty acids. These findings illustrate a dichotomy in synthesis that may result from initial fatty acid formation by preexisting spore fatty acid biosynthetic enzymes in the absence of de novo protein synthesis. Elucidation of the timing and kinetics of individual fatty acid formation provides a biochemical profile of activities directly related to membrane differentiation and cellular development.