中文摘要：

本室从西藏采集的土壤样品中分离到了一批链霉菌,利用脉冲电泳确定了其中5株链霉菌含有较小的线型质粒。【目的】克隆、测序和分析5个线型质粒的端粒。【方法】采用改良的＂在凝胶中进行DNA碱处理和限制性内切酶酶切＂的方法来克隆线型质粒的端粒DNA。【结果】克隆和测序了5个线型质粒的端粒DNA。通过与链霉菌典型端粒进行比较,发现这5个新的线型质粒的端粒序列同样含有多个回文序列。但是有的端粒保守的回文序列I不一定能够＂折返＂与内部序列配对形成＂超级发卡＂结构,回文序列的＂突出环＂不一定都为3nt。【结论】采用改良的方法克隆和鉴定了5个线型质粒新的端粒序列,这些新端粒的特征暗示：回文序列I的＂折返＂和3nt的回文序列的＂突出环＂不是端粒复制必需的。

英文摘要：

[Objective] Streptomyces strains were isolated from soil samples of Tibet,five small linear plasmids were detected by pulsed-field gel electrophoresis.[Objective ] Cloning,sequencing and analysis of telomeres of these plasmids.[Methods]The telomeres were cloned by a modified procedure— ＂alkaline treatment and enzyme digestion in gels＂.[Results]Telomeres of five linear plasmids were cloned and sequenced.Compared with the typical Streptomyces telomeres,the newly identified telomeres contained multiple palindromes,but some could not＂fold-back＂of their first conserved palindrome I with the internal palindromes to form a＂super-hairpin＂,and palindromes of some telomeres did not contain the 3-nt＂loop＂.[Conclusion]New telomere sequences were cloned by a modified procedure.Both foldingback of the telomere palindromes and 3-nt loop of palindromes varied among telomeres.