Bourgoin F, Guédon G, Pébay M, Roussel Y, Panis C, Decaris B
Laboratoire de Génétique et Microbiologie, UA INRA 952, Université Henri Poincaré Nancy I, Faculté des Sciences, Vandaevre-lès-Nancy, France.
Gene. 1996 Oct 31;178(1-2):15-23. doi: 10.1016/0378-1119(96)00316-2.
A 12-kb region of the Streptococcus thermophilus CNRZ368 chromosome was found to contain two copies of IS981 (one complete and one truncated) and three copies of ISS1 (two complete, ISS1SA and ISS1SC, and one truncated, delta ISS1SB). Comparison of the nucleotide sequences of these ISS1 elements with those of previously identified iso-ISS1 elements from Lactococcus lactis and the Enterococcus genus indicated that the ISS1 group is divided into three distinct subgroups which we have named alpha, beta and gamma. Nucleotide sequences of elements belonging to the same subgroup share more than 97% identity whereas sequences of elements from different groups share only 75-85% identity. Sequence analysis of ISS1SA and delta ISS1SB showed that they are members of the alpha group. We found that ISS1SC from S. themophilus CNRZ368, an ISS1 from L. lactis IL964 and IS946 from L. lactis TEK1 resulted from recombinations between alpha and beta elements. In addition, ISS1W from L. lactis Wg2 resulted from a recombination event between a gamma element and an ISS1 belonging to an unidentified subgroup. ISS1 sequences belonging to the alpha and beta subgroups were found in both S. thermophilus and L. lactis and gamma sequences were found in both the Enterococcus genus and L. lactis. The quasi-identity of some ISS1 elements in S. thermophilus and L. lactis and the distribution of alpha and beta elements suggest that horizontal transfer of ISS1 elements recently took place from L. lactis to S. thermophilus, two lactic acid bacteria used in the manufacture of cheeses. Since the presence of IS981 in S. thermophilus CNRZ368 also probably resulted from a horizontal transfer from L. lactis [Guédon et al. (1995) Mol. Microbiol. 16, 69-78], the 12-kb region bearing IS981 and ISS1 elements could be due to the integration of a lactococcal DNA fragment into the chromosome.
嗜热链球菌CNRZ368染色体上一个12 kb的区域被发现含有两个IS981拷贝（一个完整，一个截短）和三个ISS1拷贝（两个完整，即ISS1SA和ISS1SC，一个截短，即δISS1SB）。将这些ISS1元件的核苷酸序列与先前从乳酸乳球菌和肠球菌属中鉴定出的同型ISS1元件的序列进行比较，结果表明ISS1组可分为三个不同的亚组，我们将其命名为α、β和γ。属于同一亚组的元件的核苷酸序列具有超过97%的同一性，而来自不同组的元件的序列仅具有75 - 85%的同一性。对ISS1SA和δISS1SB的序列分析表明，它们是α组的成员。我们发现嗜热链球菌CNRZ368的ISS1SC、乳酸乳球菌IL964的一个ISS1以及乳酸乳球菌TEK1的IS946是由α和β元件之间的重组产生的。此外，乳酸乳球菌Wg2的ISS1W是由γ元件与一个属于未鉴定亚组的ISS1之间的重组事件产生的。在嗜热链球菌和乳酸乳球菌中都发现了属于α和β亚组的ISS1序列，在肠球菌属和乳酸乳球菌中都发现了γ序列。嗜热链球菌和乳酸乳球菌中一些ISS1元件的准同一性以及α和β元件的分布表明，ISS1元件最近从乳酸乳球菌水平转移到了嗜热链球菌，这两种乳酸菌都用于奶酪制造。由于嗜热链球菌CNRZ368中IS981的存在也可能是由于从乳酸乳球菌水平转移而来[Guédon等人（1995年），《分子微生物学》16，69 - 78]，携带IS981和ISS1元件的12 kb区域可能是由于一个乳球菌DNA片段整合到了染色体中。
