Germond J E, Lapierre L, Delley M, Mollet B
Nestlé Research Center, Nestec Ltd, Lausanne, Switzerland.
Mol Gen Genet. 1995 Aug 30;248(4):407-16. doi: 10.1007/BF02191640.
A new IS element (ISL3) was discovered in Lactobacillus delbrueckii subsp. bulgaricus during the characterization of the linkage relationships between the two genes important for milk fermentation, beta-galactosidase (lacZ) and the cell-wall associated protease (prtP). ISL3 is a 1494 bp element, flanked by 38 bp imperfect inverted repeats, and generates an 8 bp target duplication upon insertion. It contains one open reading frame, encoding a potential polypeptide of 434 amino acids, which shows significant homology (34% identity) to the transposase of the Leuconostoc mesenteroides element IS1165. Molecular analysis of spontaneous lacZ mutants revealed some strains that had sustained deletions of 7 to 30 kb in size, centered on and eliminating the copy of ISL3 next to lacZ. Other deletion endpoints were identified as located immediately adjacent to ISL3. Furthermore, genetic translocations that had occurred via transposition of ISL3 were observed fortuitously in cultures screened for deletion mutants. ISL3 can be found in one to several copies in various strains of L. delbrueckii. However, it was not present in other dairy lactic acid bacteria tested.
在德氏乳杆菌保加利亚亚种中发现了一个新的插入序列（ISL3），该发现源于对两个与牛奶发酵相关的重要基因——β-半乳糖苷酶（lacZ）和细胞壁相关蛋白酶（prtP）之间连锁关系的表征过程。ISL3是一个1494 bp的元件，两侧为38 bp的不完全反向重复序列，插入时会产生一个8 bp的靶标重复序列。它包含一个开放阅读框，编码一个由434个氨基酸组成的潜在多肽，该多肽与肠膜明串珠菌元件IS1165的转座酶具有显著的同源性（34%的同一性）。对自发lacZ突变体的分子分析显示，一些菌株发生了大小为7至30 kb的持续性缺失，缺失区域以lacZ旁边的ISL3拷贝为中心并将其消除。其他缺失端点被确定位于紧邻ISL3的位置。此外，在筛选缺失突变体的培养物中偶然观察到了通过ISL3转座发生的基因易位。ISL3可以在德氏乳杆菌的不同菌株中以一至多个拷贝的形式存在。然而，在测试的其他乳制品乳酸菌中未发现该序列。
