SIMILAR REGULATORY MECHANISMS DESPITE DIFFERENCES IN MEMBRANE LIPID-COMPOSITION IN ACHOLEPLASMA-LAIDLAWII STRAINS A-EF22 AND B-PG9 - A MULTIVARIATE DATA-ANALYSIS

Mycoplasmas are small, cell wall-deficient bacteria. The metabolic reg ulation of the lipid composition in the membrane of the species Achole plasma laidlawii, strains A-EF22 and B-JU, is governed mainly by the b alance between the potential formation of lamellar and nonlamellar pha se structures. However, the regulatory features have not been consiste ntly observed in the B-PG9 strain. A comparison has been performed bet ween the membrane lipid composition for strains A-EF22 and B-PG9, simu ltaneously changing eight experimental conditions known to affect the regulation and packing properties of the A-EF22 lipids. Multiple regre ssion and partial least-square discriminant analyses of many variables showed: (i) quantitative differences in membrane lipid and protein co mposition, and in membrane protein molecular masses of the two strains ; (ii) different molar fractions of the major polar lipids monoglucosy ldiacylglycerol (nonlamellar) and diglucosyldiacylglycerol (lamellar), which were caused by differences in lipid acyl chain length and unsat uration inherent in the strains and by the type of growth medium used; and (iii) similar regulatory mechanisms for changes in the lipid comp osition under most conditions, responding to the experimentally varied bilayer and nonbilayer properties of the lipid matrix. These regulato ry principles are probably valid in other bacteria as well.