A genomic island of the pathogen Leptospira interrogans serovar Lai can excise from its chromosome
A genomic island of the pathogen Leptospira interrogans serovar Lai can excise from its chromosome
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DOI：
10.1128/iai.01067-06
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发表时间：
2007-02-01
影响因子：
3.1
通讯作者：
Picardeau, Mathieu
中科院分区：
文献类型：
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作者：
Bourhy, Pascale;Salaun, Laurence;Picardeau, Mathieu
对迄今已测序的两种疑问钩端螺旋体基因组的检查显示，遗传差异很小，包括在L.疑问钩端螺旋体血清Lai中有一个长度为54 kb的额外DNA区域。该位点包含103个预测编码序列，这些序列在哥本哈根l.s审问菌血清基因组中缺失，其中只有20%在GenBank中有显著的BLASTP hit。通过脉冲场凝胶电泳分析，我们还发现这段54 kb的DNA片段以环状质粒的形式存在。如果这个区域从染色体上切除，并且它的左右两端连接在一起，则通过扩增与预测片段对应的DNA片段证实了这一点。此外，克隆该DNA区域的代表基因可在钩端螺旋体中自主复制，从而产生新的大肠埃希菌-钩端螺旋体穿梭载体。综上所述，我们的结果表明，这个基因组岛可以从染色体上切除并形成复制质粒。对该基因组岛的分布分析表明，在其他疑问乳杆菌毒力菌株中也存在高度相关的序列。这个基因组岛包含了高比例的新基因，可能在细菌种群中传播包括毒力因子在内的基因方面起着重要作用。
An examination of the two Leptospira interrogans genomes sequenced so far reveals few genetic differences, including an extra DNA region, 54 kb in length, in L. interrogans serovar Lai. This locus contains 103 predicted coding sequences that are absent from the genome of L. interrogans serovar Copenhageni, of which only 20% had significant BLASTP hits in GenBank. By analyzing the L. interrogans serovar Lai genome by pulsed-field gel electrophoresis, we also found that this 54-kb DNA fragment exists as a circular plasmid. This was confirmed by amplification of a DNA fragment corresponding to that of the predicted fragment if this region excised from the chromosome and its left and right ends joined together. In addition, cloning of the putative rep gene of this DNA region was responsible for autonomous replication in Leptospira spp., therefore generating a new Escherichia coli-Leptospira sp. shuttle vector. Taken together, our results show that this genomic island can excise from the chromosome and form a replicative plasmid. Analysis of the distribution of this genomic island revealed that highly related sequences exist in other L. interrogans virulent strains. This genomic island, containing a high proportion of novel genes, may have an important role in spreading genes, including virulence factors, among bacterial populations.