Genetic and structural analysis of the Bacteroides conjugative transposon CTn341
Genetic and structural analysis of the Bacteroides conjugative transposon CTn341
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DOI：
10.1128/jb.187.8.2858-2869.2005
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发表时间：
2005-04-01
影响因子：
3.2
通讯作者：
Smith, CJ
中科院分区：
文献类型：
--
作者：
Bacic, M;Parker, AC;Smith, CJ
确定了拟杆菌接合转座子 (CTn) CTn341 的遗传结构和功能组织。 CTn341 最初是从普通拟杆菌的四环素耐药临床分离株中分离出来的。该元件长 51,993 bp，其中包括以环状形式连接转座子末端的 5 bp 偶联序列。共有46个基因，相应的基因产物分为三大功能组：DNA代谢、调控和抗生素耐药性以及接合。在功能组中观察到的 G+C 含量和密码子使用表明这些组属于不同的遗传谱系，表明 CTn341 是一个复合的模块化元件。对代表不同功能组的基因的突变分析为基因分配提供了证据，并表明基本的接合和切除基因在拟杆菌属中是保守的。一个 IIA1 组内含子（命名为 13111）被发现被插入到 bmhA 甲基化酶基因中。 CTn341 RNA 的逆转录酶 PCR 分析表明 B.fr.11 具有功能并且是从 bmhA 基因中剪接出来的。在脆弱拟杆菌 NCTC9343 和多形拟杆菌 VP15482 的基因组序列中发现了 6 个相关的 CTn 样元件。假定的元件与 CTn341 相似，主要在 tra 和 mob 区域以及 exc 基因中，并且有几个似乎包含内含子元件。我们的数据提供了第一个报道的完整拟杆菌CTn序列，它们应该对拟杆菌中抗生素抗性元件和基因组进化的进一步功能和遗传分析具有相当大的益处。
The genetic structure and functional organization of a Bacteroides conjugative transposon (CTn), CTn341, were determined. CTn341 was originally isolated from a tetracycline-resistant clinical isolate of Bacteroides vulgatus. The element was 51,993 bp long, which included a 5-bp coupling sequence that linked the transposon ends in the circular form. There were 46 genes, and the corresponding gene products fell into three major functional groups: DNA metabolism, regulation and antibiotic resistance, and conjugation. The G+C content and codon usage observed in the functional groups suggested that the groups belong to different genetic lineages, indicating that CTn341 is a composite, modular element. Mutational analysis of genes representing the different functional groups provided evidence for the gene assignments and showed that the basic conjugation and excision genes are conserved among Bacteroides spp. A group IIA1 intron, designated 13111, was found to be inserted into the bmhA methylase gene. Reverse transcriptase PCR analysis of CTn341 RNA showed that B.fr.11 was functional and was spliced out of the bmhA gene. Six related CTn-like elements were found in the genome sequences of Bacteroides fragilis NCTC9343 and Bacteroides thetaiotaomicron VP15482. The putative elements were similar to CTn341 primarily in the tra and mob regions and in the exc gene, and several appeared to contain intron elements. Our data provide the first reported sequence for a complete Bacteroides CTn, and they should be of considerable benefit to further functional and genetic analyses of antibiotic resistance elements and genome evolution in Bacteroides.