Daveran-Mingot M L, Campo N, Ritzenthaler P, Le Bourgeois P
Laboratoire de Microbiologie et Génétique Moléculaire du CNRS, Université Paul Sabatier, 31062 Toulouse, France.
J Bacteriol. 1998 Sep;180(18):4834-42. doi: 10.1128/JB.180.18.4834-4842.1998.
Comparative analysis of chromosomal macrorestriction polymorphism of the two closely related Lactococcus lactis subsp. cremoris strains MG1363 and NCDO763 revealed the presence of a large inversion covering half of the genome. To determine what kind of genetic element could be implicated in this rearrangement, the two inversion junctions of MG1363 and NCDO763 chromosomes were cloned and characterized. Nucleotide sequence analysis showed the presence of one copy of the lactococcal IS905 element in each junction. Each copy of this element contained the same nucleotide mutation that inactivates the putative transposase. Comparison of the sequences surrounding the insertion sequence demonstrated that the large inversion arose from a single-step homologous recombination event between the two defective copies of the IS905 element. The large inversion presumably conferred no selective disadvantage on strain NCDO763 because this rearrangement did not alter the oriC-terC symmetry of the chromosome and the local genetic environment.
对两个密切相关的乳酸乳球菌亚种cremoris菌株MG1363和NCDO763的染色体宏观限制性多态性进行比较分析，发现存在一个覆盖基因组一半的大倒位。为了确定哪种遗传元件可能与这种重排有关，对MG1363和NCDO763染色体的两个倒位连接点进行了克隆和表征。核苷酸序列分析表明，每个连接点都存在一个乳酸乳球菌IS905元件拷贝。该元件的每个拷贝都含有相同的核苷酸突变，使推定的转座酶失活。对插入序列周围序列的比较表明，大倒位源于IS905元件两个缺陷拷贝之间的单步同源重组事件。大倒位可能没有给菌株NCDO763带来选择性劣势，因为这种重排没有改变染色体的oriC-terC对称性和局部遗传环境。
