School of Biological Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia.
J Basic Microbiol. 2010 Apr;50(2):179-89. doi: 10.1002/jobm.200900138.
Pseudomonas sp. USM 4-55 is a locally isolated bacterium that possesses the ability to produce polyhydroxyalkanoates (PHA) consisting of both poly(3-hydroxybutyrate) [P(3HB)] homopolymer and medium-chain length (mcl) monomers (6 to 14 carbon atoms) when sugars or fatty acids are utilized as the sole carbon source. In this study, the P(3HB) biosynthesis operon carrying the phbC(Ps) P(3HB) synthase was successfully cloned and sequenced using a homologous probe. Three open reading frames encoding NADPH-dependent acetoacetyl-coenzyme A reductase (PhbB(Ps)), beta-ketothiolase (PhbA(Ps)) and P(3HB) synthase (PhbC(Ps)) were found in the phb operon. The genetic organization of phb operon showed a putative promoter region, followed by phbB(Ps)-phbA(Ps)-phbC(Ps). phbR(Ps)which encoded a putative transcriptional activator was located in the opposite orientation, upstream of phbBAC(Ps). Heterologous expression of pGEM''ABex harboring phbC(Ps) in Escherichia coli JM109 resulted in P(3HB) accumulation of up to 40% of dry cell weight (DCW).
假单胞菌 USM 4-55 是一种具有产生聚羟基烷酸（PHA）的能力的本地分离菌，当糖或脂肪酸被用作唯一碳源时，它能够产生由聚（3-羟基丁酸酯）[P（3HB）]均聚物和中链长度（mcl）单体（6 至 14 个碳原子）组成的 PHA。在这项研究中，使用同源探针成功地克隆和测序了携带 phbC(Ps) P(3HB) 合酶的 P(3HB)生物合成操纵子。在 phb 操纵子中发现了三个编码 NADPH 依赖性乙酰乙酰辅酶 A 还原酶（PhbB(Ps)）、β-酮硫解酶（PhbA(Ps)）和 P(3HB)合酶（PhbC(Ps)）的开放阅读框。phb 操纵子的遗传组织显示出一个假定的启动子区域，随后是 phbB(Ps)-phbA(Ps)-phbC(Ps)。编码假定转录激活物的 phbR(Ps)位于相反的方向，位于 phbBAC(Ps)的上游。在大肠杆菌 JM109 中异源表达携带 phbC(Ps)的 pGEM''ABex 导致 P(3HB)积累达到干重（DCW）的 40%。
