含有大质粒的粗糙型宋内志贺氏菌的发现

The Discovery of a Large Plasmid in Rough Type Strain of Sh.sonnei

本文首次报导了一株粗糙型宋内氏菌(S_7R)中存在大质粒。试验证明,该大质粒远小于野生株中120Md 大小的 I 相质粒,只有64Md 左右,系源于有毒力的宋内志贺氏菌中的编码I相抗原及毒力的大质粒的自然缺失突变株。缺失的56Md 包含了负责编码宋内氏菌毒力和 I 相抗原的部份,编码 I 相抗原的 DNA 片段估计不大于10Md,且与毒力编码区互不相关。S_7R 株的亲本株(S_7),其 I 相大质粒既不同于 S_7R,也不同于野生型。比 S_7R 约大10Md,能正常编码宋内氏 I 相抗原;但比起野生型减小了约46Md,这与 S_7株失去所有毒力表型有关,因而该 S_7株可安全地用作组建各类具有宋内氏 I 相抗原性的痢疾菌苗的供体。S_7R 中含有大质粒的达一发现,有助于宋内氏 I 相大质粒和 I 相抗原的遗传学研究。

A large plasmid was discovered in a rough type strain of Sh.sonnei named as S_7R.The presence of the large plasmid was reported only in S form of Sh.sonnei strains, which was considered relating to the I form antigen before. The plasmld is about 64 Md in size and 56 Md smaller than I form large plasmid(120Md)in wild type,which is thought to be the deletion mutant of the wild type plasmid and was iden- tified and confirmed by experiments in our 1aboratory.It was shown that the gene regions encoding 1virulence and I form antigen were deleted from the original plasmid by about 56Md in 1ength. The large plasid in the parent S_7 strain of the S_7R type is different from S_7R and the Wild strain.It is 10Md bigger than S_7R and 46Md smaller than the wild one.It encodes I form alltigen efficiently but shows no virulence.Therefore S_7 strain cohld be used as a donor to cons- trut I form antigen-containing dysentery vaccine safely. The discovery of the large ptasmid in S_7R would be benefit to the genetical study of I form large plasmid and I form antigen.