Genomic and functional analyses of SXT, an integrating antibiotic resistance gene transfer element derived from Vibrio cholerae
Genomic and functional analyses of SXT, an integrating antibiotic resistance gene transfer element derived from Vibrio cholerae
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DOI：
10.1128/jb.184.15.4259-4269.2002
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发表时间：
2002-08-01
影响因子：
3.2
通讯作者：
Waldor, MK
中科院分区：
文献类型：
--
作者：
Beaber, JW;Hochhut, B;Waldor, MK
SXT是一个典型的接合转座子样移动的遗传元件家族，编码多种抗生素抗性基因。近年来，SXT相关的接合，自我传播的整合元件已成为亚洲霍乱弧菌广泛。我们测定了SXT与100-kb DNA序列的相似性。该元件似乎是由转座子相关的抗生素抗性基因连接到各种质粒和噬菌体相关基因，以及许多来自未知来源的基因组成的嵌合体。我们通过一步染色体基因失活技术鉴定了参与接合转移和染色体切除的SXT基因，构建了一套几乎全面的缺失。与其他接合转座子不同，SXT利用与由F质粒编码的接合系统相关的接合系统。超过一半的SXT基因组，包括含有抗生素抗性基因的复合转座子样结构，并不需要它的移动性。两个SXT基因座，指定setC和setD，其预测的氨基酸序列相似的鞭毛调节器FlhC和FlhD，被发现编码调节器，激活SXT切除和转移所需的基因的转录。另一个基因座，指定setR，其基因产物具有相似性的拟杆状噬菌体CI阻遏物，似乎也调节SXT基因的表达。
SXT is representative of a family of conjugative-transposon-like mobile genetic elements that encode multiple antibiotic resistance genes. In recent years, SXT-related conjugative, self-transmissible integrating elements have become widespread in Asian Vibrio cholerae. We have determined the similar to100-kb DNA sequence of SXT. This element appears to be a chimera composed of transposon-associated antibiotic resistance genes linked to a variety of plasmid- and phage-related genes, as well as to many genes from unknown sources. We constructed a nearly comprehensive set of deletions through the use of the one-step chromosomal gene inactivation technique to identify SXT genes involved in conjugative transfer and chromosomal excision. SXT, unlike other conjugative transposons, utilizes a conjugation system related to that encoded by the F plasmid. More than half of the SXT genome, including the composite transposon-like structure that contains its antibiotic resistance genes, was not required for its mobility. Two SXT loci, designated setC and setD, whose predicted amino acid sequences were similar to those of the flagellar regulators FlhC and FlhD, were found to encode regulators that activate the transcription of genes required for SXT excision and transfer. Another locus, designated setR, whose gene product bears similarity to lambdoid phage CI repressors, also appears to regulate SXT gene expression.