Wei M L, Webster D A, Stark B C
Department of Biological, Chemical and Physical Sciences, Illinois Institute of Technology, IIT Center, Chicago, Illinois 60616, USA.
Biotechnol Bioeng. 1998 Feb 20;57(4):477-83.
The bacterial hemoglobin from Vitreoscilla has been shown to increase growth yield and yield of genetically engineered product in Escherichia coli. To test the generality of this phenomenon, the approximately 560-bp bacterial (Vitreoscilla) hemoglobin gene (vgb) (including the native promoter), cloned into the vector pUC8 in two constructs containing about 1650 and 850 bp, respectively, of Vitreoscilla DNA downstream of vgb, was transformed into Serratia marcescens. After several transfers of the transformants on selective media, both plasmids became stable in this host and the resulting strains produced hemoglobin. Both transformants were compared, regarding growth in liquid Luria-Bertani (LB) medium, with untransformed S. marcescens and S. marcescens transformed with pUC8. The vgb-bearing strains had about 5 times lower maximum viable cell numbers than the strains without hemoglobin, but the former also had late log or early stationary phase cells that were 5-10 times larger than those of the latter. Further, on a dry cell mass basis the presence of vgb inhibited cell growth in liquid media. In contrast, growth of the vgb-bearing strains on LB plates based on cell mass (determined from colony size) was markedly enhanced compared with that of the pUC8 transformant. Respiration of the vgb-bearing strains was lower than that of the strains without vgb on a cell mass basis. These results show that the presence of vgb can have idiosyncratic effects and is not always an aid to cell growth so that its use for genetic engineering must be tested on a case by case basis.
已证明来自透明颤菌的细菌血红蛋白可提高大肠杆菌中基因工程产品的生长产量和产量。为了测试这种现象的普遍性，将大约560个碱基对的细菌（透明颤菌）血红蛋白基因（vgb）（包括天然启动子）克隆到载体pUC8中，构建了两个分别含有vgb下游约1650和850个碱基对透明颤菌DNA的构建体，并将其转化到粘质沙雷氏菌中。在选择性培养基上对转化体进行几次传代后，两种质粒在该宿主中都变得稳定，并且所得菌株产生血红蛋白。将两种转化体在液体Luria-Bertani（LB）培养基中的生长与未转化的粘质沙雷氏菌和用pUC8转化的粘质沙雷氏菌进行比较。携带vgb的菌株的最大活细胞数比没有血红蛋白的菌株低约5倍，但前者在对数后期或稳定期早期的细胞比后者大5-10倍。此外，以干细胞质量计，vgb的存在抑制了液体培养基中的细胞生长。相比之下，与pUC8转化体相比，基于细胞质量（由菌落大小确定），携带vgb的菌株在LB平板上的生长明显增强。以细胞质量计，携带vgb的菌株的呼吸作用低于没有vgb的菌株。这些结果表明，vgb的存在可能具有特殊效应，并不总是有助于细胞生长，因此其在基因工程中的应用必须逐案进行测试。
