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首页> 外文期刊>Infection and immunity >The 987P fimbrial gene cluster of enterotoxigenic Escherichia coli is plasmid encoded.
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The 987P fimbrial gene cluster of enterotoxigenic Escherichia coli is plasmid encoded.

机译：产肠毒素大肠杆菌的987P纤维基因簇是质粒编码的。

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A clone containing the 987P fimbrial gene cluster was selected from a cosmid library of total DNA of the prototype Escherichia coli strain 987 by using 987P-specific antiserum. A subclone of 12 kilobases containing all of the genes required for fimbrial expression on a nonfimbriated K-12 strain of E. coli and a DNA fragment internal to the fimbrial subunit gene were used to probe the prototype strain and various isolates of 987P-fimbriated enterotoxigenic E. coli. All strains had several plasmids, as shown by agarose gel electrophoresis, and each of five strains which expressed 987P fimbriae showed a plasmid of 35 to 40 megadaltons (MDa) hybridizing to both 987P-specific probes. Hybridization to restricted DNA of strain 987 supported a plasmid origin for the cloned 987P gene cluster. Moreover, an isogenic strain which had lost its 35-MDa plasmid was no longer capable of synthesizing fimbrial subunits, but regained fimbrial expression after reintroduction of the TnphoA (Tn5 IS50L::phoA)-tagged 35-MDa plasmid. Absence of fimbrial subunit synthesis in K-12 strains transformed with the 35-MDa plasmid alone suggested the requirement of regulatory elements existing in strain 987 but missing in K-12 strains. A probe for the heat-stable enterotoxin STIa hybridized in each of the 987P-fimbriated strains to the plasmid containing the 987P genes and in most of these strains to an additional plasmid which contained the gene for the heat-stable enterotoxin STII. Occurrence of the 987P and STIa genes on the same replicon correlates with epidemiological observations, STIa being the most prevalent toxin produced by 987P-fimbriated E. coli.
机译：通过使用987P特异性抗血清从原型大肠杆菌菌株987总DNA的粘粒文库中选择一个包含987P纤维基因簇的克隆。使用一个包含12个碱基的12碱基的亚克隆，该基因包含在非纤维化的大肠杆菌K-12菌株中纤维表达所需的所有基因，以及该纤维亚基基因内部的DNA片段，用于探测原型菌株和987P纤维化肠毒素的各种分离株大肠杆菌。如通过琼脂糖凝胶电泳所显示的，所有菌株均具有数个质粒，并且表达987P菌毛的五个菌株中的每一个均显示出与两个987P特异性探针杂交的35至40兆道尔顿（MDa）的质粒。与菌株987的限制性DNA的杂交支持了克隆的987P基因簇的质粒来源。此外，丢失了其35-MDa质粒的同基因菌株不再能够合成纤维亚基，但在重新引入标记有TnphoA（Tn5 IS50L :: phoA）的35-MDa质粒后恢复了纤维表达。仅用35-MDa质粒转化的K-12菌株缺乏纤维亚基合成，提示需要在987菌株中存在但在K-12菌株中缺少的调控元件。一种用于热稳定肠毒素STIa的探针，在每个987P克隆的菌株中与含有987P基因的质粒杂交，并且在大多数菌株中，与另一质粒杂交，该质粒包含用于热稳定肠毒素STII的基因。在同一复制子上出现987P和STIa基因与流行病学观察结果相关，STIa是由987P克隆的大肠杆菌产生的最普遍的毒素。

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