Sequencing and Diversity Analyses Reveal Extensive Similarities between Some Epsilon-Toxin-Encoding Plasmids and the pCPF5603 Clostridium perfringens Enterotoxin Plasmid
Sequencing and Diversity Analyses Reveal Extensive Similarities between Some Epsilon-Toxin-Encoding Plasmids and the pCPF5603 Clostridium perfringens Enterotoxin Plasmid
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DOI：
10.1128/jb.00939-08
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发表时间：
2008-11-01
影响因子：
3.2
通讯作者：
McClane, Bruce A.
中科院分区：
文献类型：
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作者：
Miyamoto, Kazuaki;Li, Jihong;McClane, Bruce A.
产气荚膜梭菌B型和D型分离物产生epsilon毒素，这是第三强的梭菌毒素。epsilon毒素基因（etx）在D型分离株中是质粒携带的，但在B型分离株中etx的遗传学研究很少。本研究报道了B型菌株NCTC8533的etx质粒pCP8533etx的首次测序。该etx质粒全长64.7 kb，携带tcp共轭转移基因，编码其他潜在毒力因子，包括β -毒素、分选酶和胶原粘连蛋白，但不编码β -毒素。有趣的是，近80%的pCP8533etx开放阅读框（orf）也存在于pCPF5603上，pCPF5603是A型分离物F5603的肠毒素编码质粒。脉冲场凝胶电泳和重叠PCR显示，大多数（如果不是全部）其他B型分离株和部分β 2-毒素阳性、cpe阴性的D型分离株中也存在pcp8533etx样etx质粒，而其他D型分离株携带不同的etx质粒。etx基因上游的序列在B型分离株和一些不携带pCP8533etx样质粒的D型分离株之间有所不同。然而，几乎所有的B型和D型分离株都有上游IS1151的etx位点，这些etx位点通常位于dcm ORF附近。这些结果表明，pCPF5603和pCP8533etx分别是由携带肠毒素或etx基因的移动遗传元件插入到共同的祖质粒上进化而来的。
Clostridium perfringens type B and D isolates produce epsilon- toxin, the third most potent clostridial toxin. The epsilon- toxin gene (etx) is plasmid borne in type D isolates, but etx genetics have been poorly studied in type B isolates. This study reports the first sequencing of any etx plasmid, i.e., pCP8533etx, from type B strain NCTC8533. This etx plasmid is 64.7 kb, carries tcp conjugative transfer genes, and encodes additional potential virulence factors including beta2-toxin, sortase, and collagen adhesin but not beta-toxin. Interestingly, nearly 80% of pCP8533etx open reading frames (ORFs) are also present on pCPF5603, an enterotoxin-encoding plasmid from type A isolate F5603. Pulsed-field gel electrophoresis and overlapping PCR indicated that a pCP8533etx-like etx plasmid is also present in most, if not all, other type B isolates and some beta2-toxin-positive, cpe-negative type D isolates, while other type D isolates carry different etx plasmids. Sequences upstream of the etx gene vary between type B isolates and some type D isolates that do not carry a pCP8533etx- like etx plasmid. However, nearly all type B and D isolates have an etx locus with an upstream IS1151, and those etx loci typically reside near a dcm ORF. These results suggest that pCPF5603 and pCP8533etx evolved from insertion of mobile genetic elements carrying enterotoxin or etx genes, respectively, onto a common progenitor plasmid.