富养罗尔斯通氏菌菌株PHB"泄漏"机理的初探

建立了一种分离纯化聚羟基丁酸(Polyhydroxybutyrate，PHB)颗粒的改良方法。采用这种方法从Ralstonia eutropha菌株H16(野生型)、SK1489(Tn5诱变的PHB泄漏菌株)、JMP222(野生的PHB泄漏菌株)分离了PHB颗粒。进一步比较研究了不同菌株的PHB解聚酶和3-羟基丁酸脱氢酶的活性。研究结果表明，菌株SK1489的PHB解聚酶活性(48h培养后达1．82U／mg)明显高于野生型菌株H16(48h培养后达0．37U／mg)，菌株JMP222的3-羟基丁酸脱氢酶活性(培养96h后达165．9U／mg)比菌株H16培养(96h后达64．0U／mg)高许多。这些结果显示，不同菌株PHB的泄漏有不同的原因，突变株SK1489导致PHB泄漏的原因是解聚酶活性高，而野生型JMP222PHB泄漏的原因主要是3-羟基丁酸脱氢酶活性高。

Primary Analysis on the Poly(3-hydroxybutyrate)-leaky Phenotypes of Different Ralstonia eutropha Strains

Ralstonia eutropha accumulates poly(3 hydroxybutyrate) (PHB) as intracellular carbon storage when carbon sources (e.g. gluconate) are in excess in culture medium. It catabolizes the accumulated PHB for energy and carbon when the medium is depleted of carbon sources. Intracellular PHB depolymerase and 3 hydroxybutyrate dehydrogenase catalyze the initial reactions of intracellular PHB catabolism. In this paper, a modified method for isolation of native PHB granules was established. Native PHB granules were isolated from cells of strains H16, SK1489, and JMP222 The activities of intracellular PHB depolymerase and of 3 hydroxybutyrate dehydrogenase were determined. Results indicated that the activity of intracellular PHB depolymerase of strain SK1489 was higher than that of strain H16, and the activity of 3 hydroxybutyrate dehydrogenase of strain JMP222 was much higher than that of strain H16 Based on these results it is concluded that the PHB leaky phenotypes were attributed to the higher activities of intracellular PHB depolymerase and 3 hydroxybutyrate dehydrogenase for strains SK1489 and JMP222, respectively.