CONICET | Buscador de Institutos y Recursos Humanos

Members of the genera Rhodococcus and Nocardia corallina were investigated foT their capability to accumulate storage lipids that occur in the cytoplasm during cultivation of the cells under nitrogen-limiting conditions in the absence or presence of various effectors. All bacteria were able to accumulate triacylglycerols (TAG) as main compounds plus minor amounts of diacylglycerols and wax esters. In addition to neutral lipids, R. jascians, R. erythropolis, and R. opacus MR22 accumulated 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 inhibitors of the citric acid cycle, caused a decrease in the content of odd-numbered fatty acids in the TAG accumulated from acetate by R. opacus PD630. Cerulenin, an inhibitor ofthe fattyacid de nova synthesis, completely inhibited accumulation ofTAG from glucose or gluconate but not 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. corallina. Acrylic acid, an inhibitor of fatty acid p -oxidation, completely or partially inhibited accumulation of TAG from hexadecane or valerate, respectively, in R. opacus PD630. In R. ruber, acrylic acid completely inhibited accumulations of TAG from valerate; under these conditions 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 of3HV units into the PHA in R. ruber. Therefore, the relative amounts and compositions of both storage lipids can be affected by various compounds in these Gram-positive bacteria.

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