Polyhydroxyalkanoates (PHAs) are biodegradable bioplastics that are synthesized by diverse bacteria. In this study, the synthesis of PHAs by the model aromatic-degrading strain Burkholderia xenovorans LB400 was analyzed. Twelve pha genes including three copies of phaC and five copies of the phasin-coding phaP genes are distributed among the three LB400 replicons. The phaC1ABR gene cluster that encodes the enzymes of the PHA anabolic pathway is located at chromosome 1 of strain LB400. During the growth of strain LB400 on glucose under nitrogen limitation, the expression of the phaC1, phaA, phaP1, phaR, and phaZ genes was induced. Under nitrogen limitation, PHA accumulation in LB400 cells was observed by fluorescence microscopy after Nile Red staining. GC-MS analyses revealed that the PHA accumulated under nitrogen limitation was poly(3-hydroxybutyrate) (PHB). LB400 cells grown on glucose as the sole carbon source under nitrogen limitation accumulated 40 ± 0.96% PHB of the cell dry weight, whereas no PHA was observed in cells grown in control medium. The functionality of the phaC1 gene from strain LB400 was further studied using heterologous expression in a Pseudomonas putida KT40C1ZC2 mutant strain derived from P. putida KT2440 that is unable to synthesize PHAs. Interestingly, KT40C1ZC2[pVNC1] cells that express the phaC1 gene from strain LB400 were able to synthesize PHB (33.5% dry weight). This study indicates that B. xenovorans LB400 possesses a functional PHA synthetic pathway that is encoded by the pha genes and is capable of synthesizing PHB.

中文翻译：

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异种伯克霍尔德氏菌LB400具有由pha基因编码的功能性聚羟基链烷酸酯合成代谢途径，并在氮限制条件下合成聚3-羟基丁酸酯。

聚羟基链烷酸酯（PHA）是由多种细菌合成的可生物降解的生物塑料。在这项研究中，分析了模型降解芳香族伯克霍尔德菌xenovorans LB400的PHAs的合成。在三个LB400复制子中分布了十二个pha基因，其中包括phaC的三个拷贝和phasin编码的phaP基因的五个拷贝。编码PHA同化途径酶的phaC1ABR基因簇位于LB400菌株的1号染色体上。在应变LB400对葡萄糖在氮气不限于，表达的生长phaC1，PHAA，phaP1，药业和pha Z基因被诱导。在氮限制下，尼罗红染色后通过荧光显微镜观察了LB400细胞中的PHA积累。GC-MS分析表明，在氮限制下积累的PHA是聚（3-羟基丁酸酯）（PHB）。在氮限制下，以葡萄糖作为唯一碳源生长的LB400细胞积累了40±0.96％的干重PHB，而在对照培养基中生长的细胞中未观察到PHA。使用异源表达在不能合成PHA的恶臭假单胞菌KT2440衍生的恶臭假单胞菌KT40 C1ZC2突变株中使用异源表达进一步研究了菌株LB400的phaC1基因的功能。有趣的是，KT40C1ZC2 [pVNC1]细胞表达LB400菌株的phaC1基因能够合成PHB（33.5％干重）。这项研究表明，异种双歧杆菌LB400具有功能性的PHA合成途径，该途径由pha基因编码，并且能够合成PHB。