Accumulation of storage lipids in species of Rhodococcus and Nocardia and effect of inhibitors and polyethylene glycol

Members of the genera Rhodococcus and Nocardia corallina were investigated for 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. fascians, 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 of the fatty acid de novo synthesis, completely inhibited accumulation of TAG 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 β-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 of 3HV 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. Anhaufung von Speicherlipiden in den Gattungen Rhodococcus und Nocardia und Einflus von Inhibitoren und Polyethylenglykol. Vertreter der Gattungen Rhodococcus und Nocardia corallina wurden auf ihre Fahigkeit, Speicherlipide im Cytoplasma wahrend der Kultivierung unter stickstofflimitierenden Bedingungen in Gegenwart oder Abwesenheit verschiedener Effektoren zu akkumulieren, untersucht. Alle untersuchten Bakterien akkumulierten Triglyceride (TG) als Hauptkomponente sowie als Nebenkomponenten zusatzlich Diglyceride und Wachsester. R. fascians, R. erythropolis und R. opacus MR22 akkumulierten daruber hinaus geringe Mengen Poly(3-Hydroxybuttersaure), (PHB) wahrend N. corallina und R. ruber daruber hinaus betrachtliche Mengen Polyhydroxyalkanoate (PHA) bestehend aus 3-Hydroxybuttersaure (3HB) und 3-Hydroxyvaleriansaure (3HV) ausgehend von Glucose oder Valeriansaure akkumulierten. Alloxan und 3-Nitropropionsaure, Inhibitoren des Zitronensaurezyklus, bewirkten eine Abnahme des Gehalts von Fettsauren mit ungerader Anzahl von C-Atomen in den TG in Acetatzellen von R. opacus PD630. Cerulenin, ein Hemmstoff der Fettsauresynthese, unterdruckte die Akkumulation von TG ausgehend von Glucose oder Gluconsaure, aber nicht von Hexadecan in allen untersuchten Bakterien vollstandig. Cerulenin bewirkte daruber hinaus einen Anstieg des PHB-Gehalts und in R. ruber sowie N. corallina auch einen Anstieg des relativen Gehalts an 3HB in Copolyester. Acrylsaure, ein Inhibitor der β-Oxidation, hemmte in R. opacus PD630 partiell die Akkumulation von TG ausgehend von Valeriansaure. In R. ruber wurde die Akkumulation von TG ausgehend von Valeriansaure vollstandig gehemmt; unter diesen Bedingungen verdoppelte sich der PHA-Gehalt, und der Polyester bestand ausschlieslich aus 3HV. Der Zusatz von PEG-200 (0,2 bis 5%, w/v) fuhrte zu niedrigeren PHA-Gehalten der Zellen von R. ruber, stimulierte aber den Einbau von 3HV in PHA. Diese Untersuchungen zeigen, das die relativen Gehalte und die Zusammensetzungen beider Speicherlipide in diesen Gram-positiven Bakterien durch verschiedene Komponenten beeinflust werden konnen.

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