JBC, Vol. 250, Issue 22, 8720-8727, Nov, 1975
Inhibition of growth of microbial mutants by trans-octadecenoates
G. Vandenhoff, F. D. Gunstone, J. Barve and W. E. Lands
A series of positional isomers of trans-octadecenoic acid were tested for
their ability to support growth of microbial mutants that could not
synthesize unsaturated fatty acids. The bacterial strain used (a variant of
Escherichia coli 30E) grew with supplements of the trans isomers only at
high temperatures (38 degrees) and with acids containing the
trans-ethylenic bond between carbon atoms 8 through 13. The yeast mutant
(Saccharomyces cerevisiae KD46) grew only with the 9-trans-octadecenoate
giving cell yields about one-fifth those obtained with oleate. Although the
trans isomers had little effect on the growth of the bacteria in the
presence of oleate, they inhibited the growth of yeast with oleate.
Inhibition was strongest for the 4, 6, 7, 11, and 12 isomers, almost
negligible for the 8 isomer and of differing intermediate degrees for the
others. The inhibitory effects had no correlation with the melting points
of the acids and appeared to reflect selective action(s) on the metabolism
of the cell. When the net yield of the yeast cultures with oleate was
lowered by the effect of added trans acids, there was a marked accumulation
of triglycerides and nonesterified acids in the cells. The marked increase
in triglyceride content while phospholipid per cell remained relatively
constant suggest that trans acids, in addition to forming inadequate
membrane lipids, may also interfere with a basic control point in lipid
metabolism.
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