Quantitative effects of unsaturated fatty acids in microbial mutants. VI. Selective growth responses of yeast and bacteria to cis-octadecenoate isomers

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Abstract
The full series of positional isomers of cis-octadecenoate were tested for their suitability in meeting the nutritional requirements for unsaturated fatty acids by mutants of Escherichia coli and Saccharomyces cerevisiae that were unable to synthesize unsaturated fatty acids. Quantitative comparisons of the efficiencies of the various isomers showed a range of 0-48 cells/femtomol for the prokaryotic cells and 0-5 for eukaryotic cells. The .DELTA.5 isomer was much more effective than the .DELTA.6 isomer with the bacterial cells; the reverse was true with the yeast cells. Isomers comtaining a cis ethylenic bond between carbons 7 and 12 were generally able to support extensive growth of either type of mutant. Since all of the various isomers were incorporated into cellular lipids by both microorganisms the different efficiencies observed in supporting growth were not a simple reflection of the inability of an acid to be esterified. The differences may reflect the suitability of the resultant esterified product to function as a normal membrane lipid. The contents of various fatty acids in the cellular phospholipids when growth ceases may have a linearly cumulative relationship to the degree of expansion of the acyl chains.

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