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DNA Research Advance Access originally published online on September 18, 2009
DNA Research 2009 16(5):299-309; doi:10.1093/dnares/dsp015
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© The Author 2009. Published by Oxford University Press on behalf of Kazusa DNA Research Institute
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Short Communication

Nucleotide sequence analysis of the enterotoxigenic Escherichia coli Ent plasmid

Sadayuki Ochi1,*, Tohru Shimizu2, Kaori Ohtani2, Yoshio Ichinose3, Hideyuki Arimitsu1, Kentaro Tsukamoto1, Michio Kato1 and Takao Tsuji1

1 Department of Microbiology, School of Medicine, Fujita Health University, Toyoake, Aichi 470-1192, Japan
2 Department of Microbiology, Graduate School of Medical Science, Kanazawa University, Kanazawa, Ishikawa 920-8640, Japan
3 Department of Eco- epidemiology, Kenya Research Station, Institute of Tropical Medicine, Nagasaki University, Sakamoto, Nagasaki 852-8523, Japan

Received 11 March 2009 ; accepted 10 August 2009.

We report here the complete nucleotide sequence of pEntH10407 (65 147 bp), an enterotoxigenic Escherichia coli enterotoxin plasmid (Ent plasmid), which is self-transmissible at low frequency. Within the plasmid, we identified 100 open reading frames (ORFs) which could encode polypeptides. These ORFs included regions encoding heat-labile (LT) and heat-stable (STIa) enterotoxins, regions encoding tools for plasmid replication and an incomplete tra (conjugation) region. The LT and STIa region was located 13.5 kb apart and was surrounded by three IS1s and an IS600 in opposite reading orientations, indicating that the enterotoxin genes may have been horizontally transferred into the plasmid. We identified a single RepFIIA replication region (2.0 kb) including RepA proteins similar to RepA1, RepA2, RepA3 and RepA4. The incomplete tra region was made up of 17 tra genes, which were nearly identical to the corresponding genes of R100, and showed evidence of multiple insertions of ISEc8 and ISEc8-like elements. These data suggest that pEntH10407 has the mosaic nature characteristic of bacterial virulence plasmids, which contains information about its evolution. Although the tra genes might originally have rendered pEntH10407 self-transferable to the same degree as R100, multiple insertion events have occurred in the tra region of pEntH10407 to make it less mobile. Another self-transmissible plasmid might help pEntH10407 to transfer efficiently into H10407 strain. In this paper, we suggest another possibility: that the enterotoxigenic H10407 strain might be formed by auto-transfer of pEntH10407 at a low rate using the incomplete tra region.

Key words: enterotoxin gene; pathogenicity islet; virulence plasmid

* To whom correspondence should be addressed. Tel. +81 562-93-2433. Email: ochi{at}fujita-hu.ac.jp


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