
Full text loading...
The octadecenoic acid growth-requirement for Acholeplasma (Mycoplasma) laidlawii a can be effectively replaced by cis-9,10-methylenehexadecanoic acid but not by m-9,10-hexadecenoic acid. Once incorporated into the membrane polar lipids, this acid is also elongated to cis-11,12-methyleneoctadecanoic acid. This is the first instance of the elongation of a cyclopropane fatty acid by a microorganism. cis-9,10-Methylenehexadecanoic acid, like cis-9,10-octadecenoic acid, alters the osmotic fragility of this mycoplasma, but while a correlation exists between fatty acid concentration and yield of organism, there is no apparent relationship between fatty acid concentration, maximal yield and greatest membrane osmotic stability for this organism. The fatty acid composition of the membrane polar lipids of A. laidlawii a grown with cis-11,12-octadecenoic and cis-9,10-methylenehexadecanoic acids shows each acid to be incorporated to a similar extent. A cell-free system from A. laidlawii a synthesized less cw-11,12- methyleneoctadecanoic and tetradecanoic acids but more octadecanoic acid when compared with the fatty acid composition of the intact organism.