Comparison of virulence plasmids among Clostridium perfringens type E isolates
Comparison of virulence plasmids among Clostridium perfringens type E isolates
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DOI：
10.1128/iai.01981-06
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发表时间：
2007-04-01
影响因子：
3.1
通讯作者：
McClane, Bruce A.
中科院分区：
文献类型：
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作者：
Li, Jihong;Miyamoto, Kazuaki;McClane, Bruce A.
E型产气荚膜梭菌产生IOTA毒素，该毒素由IAP和IBP基因编码。通过Southern杂交分析，本研究在8株E型分离株中鉴定出与97或135kb相似的IAP/IBP质粒。对于这些分离株中的大多数，他们的iaplibp质粒还编码尿素酶和波长毒素。然而，如果存在Beta2毒素基因，则该基因位于与iapliBP不同的质粒上。对于所有的分离株，iapliBP质粒携带一个tcp基因座，强烈地表明这些质粒是接合的。重叠的聚合酶链式反应分析表明，A型分离株的iaplibp与肠毒素编码的质粒有一定的相似性。进一步的聚合酶链式反应分析表明，iapliBP基因座位于DCM序列附近，这是一个明显的毒素基因插入的质粒热点，iapliBP基因座上存在两个与IS1151相关的序列。为了开始测试这些类似IS1151的序列是否可以动员iapliBP基因，进行了一项仅从代表转座中间产物的环状DNA形式中扩增产物的聚合酶链式反应。这种聚合酶链式反应检测到含有iapliBP基因和沉默的肠毒素基因序列的环状形式，带有或不带有类似IS1151的序列。综上所述，这些结果表明，携带iapliBP的移动遗传元件已插入到A型分离株中携带tcp的肠毒素质粒上，创建了前体iapliBP质粒。然后，该质粒通过接合传播到其他分离物，将它们转化为E型。当iapliBP基因后来重新激活并插入到其他接合质粒上时，或者当一些iapliBP质粒获得额外的DNA序列时，iapliBP质粒多样性发生。
Clostridium perftingens type E isolates produce iota-toxin, which is encoded by iap and ibp genes. Using Southern blot analyses, the current study identified iap/ibp plasmids of similar to 97 or similar to 135 kb among eight type E isolates. For most of these isolates, their iaplibp plasmid also encoded urease and lambda-toxin. However, the beta2-toxin gene, if present, was on a different plasmid from the iaplibp plasmid. For all isolates, the iaplibp plasmid carried a tcp locus, strongly suggesting that these plasmids are conjugative. Overlapping PCR analyses demonstrated some similarity between the iaplibp plasmids and enterotoxin-encoding plasmids of type A isolates. Additional PCR analyses demonstrated that the iaplibp locus is located near dcm sequences, an apparent plasmid hot spot for toxin gene insertion, and that two IS1151-related sequences are present in the iaplibp locus. To begin testing whether those IS1151-like sequences can mobilize iaplibp genes, a PCR assay was performed that amplifies a product only from circular DNA forms that could represent transposition intermediates. This PCR assay detected circular forms containing iaplibp genes and silent enterotoxin gene sequences, with or without an IS1151-like sequence. Collectively, these results suggest that a mobile genetic element carrying iaplibp has inserted onto a tcp-carrying enterotoxin plasmid in a type A isolate, creating a progenitor iaplibp plasmid. That plasmid then spread via conjugation to other isolates, converting them to type E. Further iaplibp plasmid diversity occurred when either the iaplibp genes later remobilized and inserted onto other conjugative plasmids or some iaplibp plasmids acquired additional DNA sequences.