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

Abstract

The biosynthesis of individual branchedand 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-C18,, i-C14, and i-C1*; no normal or anteiso synthesis occurs. Subsequent to T8,s the full complement of branchedand 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.

Incorporation of Specific Fatty Acid Precursors During Spore Germination and Outgrowth in Bacillus thuringiensis

“…As indicated by the different pulse times, incorporation of these precursors differs during germination and during outgrowth. Of course, the normal-odd fatty acids are not synthesized unless precursors such as propionate or valerate are added exogenously (9,10). The relative proportions within each family of fatty acids, e.g., i-C13, i-C15, i-C17, were very similar to those we observed previously (10) with radioactive acetate.…”

“…Of course, the normal-odd fatty acids are not synthesized unless precursors such as propionate or valerate are added exogenously (9,10). The relative proportions within each family of fatty acids, e.g., i-C13, i-C15, i-C17, were very similar to those we observed previously (10) with radioactive acetate. Also, we very recently observed efficient incorporation of '4C-isoleucine into anteiso-isomers (data not shown).…”

“…Spores of B. thuringiensis were germinated as previously described (10,11). Four individual pulses of 30 min were employed for each of the on September 1, 2020 by guest http://aem.asm.org/ Downloaded from specific precursors.…”

“…Because the radioactive precursors were added in low concentration without accompanying carrier, the overall fatty acid composition of the cells remained unchanged. Subsequently, the fatty acids were extracted and converted to their methyl esters, and the extent of precursor incorporation into specific fatty acids was determined on a gas chromatograph interfaced to a liquid scintillation counter (10,14). Efficiency of recovery of radioactively labeled fatty acids was about 75% using this technique.…”

Sporulation in Bacillus subtilis is independent of membrane fatty acid composition

“…Although the bfmB mutant could use diverse fatty acids for growth and sporulation, it was possible that certain types of fatty acids were preferentially incorporated into the membranes of vegetative cells or spores. Such differential fatty acid synthesis occurs during the germination of B. thuringiensis (13). To examine this, cultures of the bfmB mutant (61539) were supplemented with 0.1 mM isobutyrate, isovalerate, or 2-methylbutyrate, and the fatty acid content of these cells was determined during growth and sporulation (Fig.…”