Le Bourgeois P, Lautier M, van den Berghe L, Gasson M J, Ritzenthaler P
Laboratoire de Microbiologie et Génétique Moléculaire, Institut de Biologie Cellulaire et de Génétique du Centre National de la Recherche Scientifique, Toulouse, France.
J Bacteriol. 1995 May;177(10):2840-50. doi: 10.1128/jb.177.10.2840-2850.1995.
A physical and genetic map of the chromosome of the Lactococcus lactis subsp. cremoris reference strain MG1363 was established. The physical map was constructed for NotI, ApaI, and SmaI enzymes by using a strategy that combines creation of new rare restriction sites by the random-integration vector pRL1 and ordering of restriction fragments by indirect end-labeling experiments. The MG1363 chromosome appeared to be circular and 2,560 kb long. Seventy-seven chromosomal markers were located on the physical map by hybridization experiments. Integration via homologous recombination of pRC1-derived plasmids allowed a more precise location of some lactococcal genes and determination of their orientation on the chromosome. The MG1363 chromosome contains six rRNA operons; five are clustered within 15% of the chromosome and transcribed in the same direction. Comparison of the L. lactis subsp. cremoris MG1363 physical map with those of the two L. lactis subsp. lactis strains IL1403 and DL11 revealed a high degree of restriction polymorphism. At the genetic organization level, despite an overall conservation of gene organization, strain MG1363 presents a large inversion of half of the genome in the region containing the rRNA operons.
构建了乳酸乳球菌乳脂亚种参考菌株MG1363的染色体物理图谱和遗传图谱。物理图谱是通过一种策略构建的，该策略结合了利用随机整合载体pRL1创建新的稀有限制酶切位点以及通过间接末端标记实验对限制片段进行排序，所用酶为NotI、ApaI和SmaI。MG1363染色体似乎是环状的，长度为2560 kb。通过杂交实验在物理图谱上定位了77个染色体标记。通过同源重组将源自pRC1的质粒整合，使得一些乳球菌基因的定位更加精确，并确定了它们在染色体上的方向。MG1363染色体包含6个rRNA操纵子；其中5个聚集在染色体的15%范围内，并以相同方向转录。将乳酸乳球菌乳脂亚种MG1363的物理图谱与两株乳酸乳球菌乳酸亚种菌株IL1403和DL11的物理图谱进行比较，发现存在高度的限制酶切多态性。在基因组织水平上，尽管基因组织总体上保守，但MG1363菌株在包含rRNA操纵子的区域存在基因组一半的大倒位。
