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Genetic Structure and Distribution of the Colibactin Genomic Island among Members of the Family Enterobacteriaceae

机译:肠杆菌科成员中colibactin基因岛的遗传结构和分布

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摘要

A genomic island encoding the biosynthesis and secretion pathway of putative hybrid nonribosomal peptide-polyketide colibactin has been recently described in Escherichia coli. Colibactin acts as a cyclomodulin and blocks the eukaryotic cell cycle. The origin and prevalence of the colibactin island among enterobacteria are unknown. We therefore screened 1,565 isolates of different genera and species related to the Enterobacteriaceae by PCR for the presence of this DNA element. The island was detected not only in E. coli but also in Klebsiella pneumoniae, Enterobacter aerogenes, and Citrobacter koseri isolates. It was highly conserved among these species and was always associated with the yersiniabactin determinant. Structural variations between individual strains were only observed in an intergenic region containing variable numbers of tandem repeats. In E. coli, the colibactin island was usually restricted to isolates of phylogenetic group B2 and inserted at the asnW tRNA locus. Interestingly, in K. pneumoniae, E. aerogenes, C. koseri, and three E. coli strains of phylogenetic group B1, the functional colibactin determinant was associated with a genetic element similar to the integrative and conjugative elements ICEEc1 and ICEKp1 and to several enterobacterial plasmids. Different asn tRNA genes served as chromosomal insertion sites of the ICE-associated colibactin determinant: asnU in the three E. coli strains of ECOR group B1, and different asn tRNA loci in K. pneumoniae. The detection of the colibactin genes associated with an ICE-like element in several enterobacteria provides new insights into the spread of this gene cluster and its putative mode of transfer. Our results shed light on the mechanisms of genetic exchange between members of the family Enterobacteriaceae.
机译:最近在大肠杆菌中已经描述了编码假定的杂种非核糖体肽-聚酮大肠菌素的生物合成和分泌途径的基因组岛。 Colibactin充当环调节蛋白并阻断真核细胞周期。肠杆菌中大肠菌素岛的起源和流行情况尚不清楚。因此,我们通过PCR筛选了与肠杆菌科相关的不同属和种的1,565个分离株,以寻找该DNA元件的存在。该岛不仅在大肠杆菌中发现,而且在肺炎克雷伯菌,产气肠杆菌和科氏柠檬酸杆菌中也被检测到。在这些物种中它是高度保守的,并且始终与耶尔西菌素决定簇有关。仅在包含可变数目的串联重复的基因间区域中观察到了各个菌株之间的结构变异。在大肠杆菌中,大肠埃希菌素岛通常仅限于系统发育组B2的分离株,并插入asnW tRNA基因座。有趣的是,在肺炎克雷伯菌,产气链球菌,科氏杆菌和三个系统发育组B1的大肠杆菌菌株中,功能性大肠杆菌素决定簇与类似于整合和结合元件ICEEc1和ICEKp1的遗传元件以及多个肠杆菌相关。质粒。在三个 E中,不同的asn tRNA基因充当了ICE相关大肠菌素决定簇asnU的染色体插入位点。 ECOR B1组的大肠杆菌菌株和 K中的不同 asn tRNA位点。肺炎。对几种肠杆菌中与ICE样元件相关的大肠菌素基因的检测,为对该基因簇的扩散及其假定的转移方式提供了新的见解。我们的研究结果揭示了肠杆菌科家族成员之间的遗传交换机制。

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