Nikel Pablo I, Pettinari M Julia, Galvagno Miguel A, Méndez Beatriz S
Departamento de Química Biológica. Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria-Pabellón 2, 1428 Buenos Aires, Argentina.
Appl Environ Microbiol. 2006 Apr;72(4):2614-20. doi: 10.1128/AEM.72.4.2614-2620.2006.
We assessed the effects of different arcA mutations on poly(3-hydroxybutyrate) (PHB) synthesis in recombinant Escherichia coli strains carrying the pha synthesis genes from Azotobacter sp. strain FA8. The arcA mutations used were an internal deletion and the arcA2 allele, a leaky mutation for some of the characteristics of the Arc phenotype which confers high respiratory capacity. PHB synthesis was not detected in the wild-type strain in shaken flask cultures under low-oxygen conditions, while ArcA mutants gave rise to polymer accumulation of up to 24% of their cell dry weight. When grown under microaerobic conditions in a bioreactor, the arcA deletion mutant reached a PHB content of 27% +/- 2%. Under the same conditions, higher biomass and PHB concentrations were observed for the strain bearing the arcA2 allele, resulting in a PHB content of 35% +/- 3%. This strain grew in a simple medium at a specific growth rate of 0.69 +/- 0.07 h(-1), whereas the deletion mutant needed several nutritional additives and showed a specific growth rate of 0.56 +/- 0.06 h(-1). The results presented here suggest that arcA mutations could play a role in heterologous PHB synthesis in microaerobiosis.
我们评估了不同的arcA突变对携带来自固氮菌属菌株FA8的pha合成基因的重组大肠杆菌菌株中聚（3-羟基丁酸酯）（PHB）合成的影响。所使用的arcA突变是一个内部缺失和arcA2等位基因，arcA2等位基因对于赋予高呼吸能力的Arc表型的某些特征而言是一个渗漏突变。在低氧条件下的摇瓶培养中，野生型菌株未检测到PHB合成，而ArcA突变体导致聚合物积累量高达其细胞干重的24%。当在生物反应器中微需氧条件下生长时，arcA缺失突变体的PHB含量达到27%±2%。在相同条件下，携带arcA2等位基因的菌株观察到更高的生物量和PHB浓度，导致PHB含量为35%±3%。该菌株在简单培养基中以0.69±0.07 h⁻¹的比生长速率生长，而缺失突变体需要几种营养添加剂，并且比生长速率为0.56±0.06 h⁻¹。此处给出的结果表明，arcA突变可能在微需氧条件下的异源PHB合成中发挥作用。
