Zuerner Richard L, Trueba Gabriel A
National Reference Center for Leptospirosis, Bacterial Diseases of Livestock Research Unit, National Animal Disease Center, USDA, ARS, P.O. Box 70, Ames, IA 50010, USA.
FEMS Microbiol Lett. 2005 Jul 15;248(2):199-205. doi: 10.1016/j.femsle.2005.05.039.
Leptospira interrogans is a diverse species in which individual serovars have distinctive restriction fragment length polymorphisms that are useful in strain identification. Many of these polymorphisms can be detected using hybridization probes derived from insertion sequences; an observation that suggests these IS elements are active and can transpose in L. interrogans. Two spontaneous mutants of L. interrogans serovar Pomona strain RZ11 were isolated by immune selection and characterized. Changes in the size and antigenicity of LPS from these mutants were detected. Genetic analysis showed that both mutants have additional copies of an IS3-like element, designated IS1501, that are not present in the parental strain. One mutant, GT211, has a single additional copy of IS1501, whereas the other mutant, GT210 has three additional copies of IS1501 relative to strain RZ11. IS1501 transposition generated 3-bp direct repeats from target sequences flanking the insertion site. RT-PCR analysis of transcripts at altered loci showed IS1501 transcripts extended into adjacent sequences. These data are the first to show spontaneous transposition of an endogenous Leptospira insertion sequence, and suggest that IS1501 may be capable of gene activation.
问号钩端螺旋体是一个多样化的物种，其中各个血清型具有独特的限制性片段长度多态性，这在菌株鉴定中很有用。这些多态性中的许多可以使用源自插入序列的杂交探针来检测；这一观察结果表明这些插入序列元件是活跃的，并且可以在问号钩端螺旋体中发生转座。通过免疫选择分离并鉴定了问号钩端螺旋体波摩那血清型菌株RZ11的两个自发突变体。检测到这些突变体中脂多糖的大小和抗原性发生了变化。遗传分析表明，两个突变体都有一个类似IS3的元件的额外拷贝，命名为IS1501，而亲本菌株中不存在该元件。一个突变体GT211有一个IS1501的额外拷贝，而另一个突变体GT210相对于菌株RZ11有三个IS1501的额外拷贝。IS1501转座从插入位点两侧的靶序列产生了3 bp的直接重复序列。对改变位点的转录本进行的逆转录聚合酶链反应（RT-PCR）分析表明，IS1501转录本延伸到相邻序列中。这些数据首次显示了内源性钩端螺旋体插入序列的自发转座，并表明IS1501可能能够激活基因。
