Sakurai N, Imai Y, Komatsubara S
Research Laboratory of Applied Biochemistry, Tanabe Seiyaku Co., Ltd., Osaka, Japan.
J Biotechnol. 1995 Nov 21;43(1):11-9. doi: 10.1016/0168-1656(95)00103-9.
The growth of a d-biotin-producing strain of Serratia marcescens (SB412) was strongly inhibited by the introduction of pLGM412, a low-copy-number plasmid containing the complete biotin (bio) operon derived from SB412, whereas the wild-type strain was not inhibited by the plasmid. SB412 carrying pLGM412 was genetically unstable; large colonies appeared spontaneously from the background small colonies. When the plasmids from the large colonies were transformed into the SB412 host, all of the resultant transformants showed a large-colony phenotype, suggesting that the large-colony phenotype is due to mutations in the plasmid-born bio genes. Some of these plasmids were structurally altered and the others were not. Furthermore, the structurally altered plasmids were classified into a deleted and an elongated type. All of the mutated pLGM412 derivatives reduced or lacked the bio gene expression, indicating that the high expression of bio gene(s) causes the growth inhibition. By subcloning experiments, biotin synthase (the bioB gene product) was responsible for the growth inhibition.
将含有源自粘质沙雷氏菌（SB412）的完整生物素（bio）操纵子的低拷贝数质粒pLGM412导入产d-生物素的粘质沙雷氏菌菌株（SB412）后，其生长受到强烈抑制，而野生型菌株不受该质粒的抑制。携带pLGM412的SB412在遗传上不稳定；在背景小菌落中会自发出现大菌落。当将大菌落中的质粒转化到SB412宿主中时，所有产生的转化子都表现出大菌落表型，这表明大菌落表型是由于质粒携带的bio基因发生了突变。这些质粒中有些在结构上发生了改变，有些则没有。此外，结构改变的质粒被分为缺失型和延长型。所有突变的pLGM412衍生物都降低或缺乏bio基因表达，表明bio基因的高表达会导致生长抑制。通过亚克隆实验，生物素合酶（bioB基因产物）是导致生长抑制的原因。
