ACCUMULATION OF STORAGE LIPIDS IN SPECIES OF RHODOCOCCUS AND NOCARDIAAND EFFECT OF INHIBITORS AND POLYETHYLENE-GLYCOL

Members of the genera Rhodococcus and Nocardia corallina were investig ated for their capability to accumulate storage lipids that occur in t he cytoplasm during cultivation of the cells under nitrogen-limiting c onditions in the absence or presence of various effecters. All bacteri a were able to accumulate triacylglycerols (TAG) as main compounds plu s minor amounts of diacylglycerols and wax esters. In addition to neut ral lipids, R. fascians, R. erythropolis, and R, opacus MR22 accumulat ed small amounts of polyhydroxybutyrate (PHB), and N. corallina and R. ruber accumulated significant amounts of polyhydroxyalkanoates (PHA) consisting of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) from glucose or valerate. Alloxan or 3-nitropropionate, which are inhibito rs of the citric acid cycle, caused a decrease in the content of odd-n umbered fatty acids in the TAG accumulated from acetate by R. opacus P D630. Cerulenin, an inhibitor of the fatty acid de novo synthesis, com pletely inhibited accumulation of TAG from glucose or gluconate but no t from hexadecane in all bacteria investigated. In addition, cerulenin caused an increase of the PHA content and resulted in an increase of the relative amounts of 3HB units in the PHA in R. ruber and N. corall ina. Acrylic acid, an inhibitor of fatty acid beta-oxidation, complete ly or partially inhibited accumulation of TAG from hexadecane or valer ate, respectively, in R, opacus PD630. In R. ruber, acrylic acid compl etely inhibited accumulations of TAG from valerate; under these condit ions the content of PHA increased twofold, and the polyester consisted exclusively of 3HV. PEG-200 (0.2 to 5%, w/v) caused a decrease in the PHA content, but stimulated the incorporation of 3HV units into the P HA in R. ruber. Therefore, the relative amounts and compositions of bo th storage lipids can be affected by various compounds in these Gram-p ositive bacteria.