中文摘要：

近年来，随着大质粒提取和检测技术的发展，尤其是高通量DNA测序技术的应用，使得链霉菌大的环型质粒和线型质粒的研究取得了较快的进展。相比于研究透彻的细菌Theta型复制的质粒，链霉菌Theta型质粒在复制区的结构、复制蛋白和调控蛋白作用的分子机理等方面具有多样性和新颖性。新鉴定的许多线型质粒的中心复制区表明中心复制的起始可以靠近端粒，一个质粒也可以有2个以上的复制区。新分离的端粒序列显示端粒“折返”不是必需的，而形成二级结构对于端粒复制是重要的。链霉菌环型和线型质粒的测序分析显示它们之间存在亲缘关系。环型质粒可以与噬菌体共整合，实验证明它们在一定条件下可以相互转换。这些研究结果表明，链霉菌环型、线型质粒和噬茵体从结构到功能到进化具有多样性、新颖性开口亲缘关系。

英文摘要：

Recently, with the development of isolating and detecting large plasmids and high-throughput DNA sequencing technology, rapid progresses have been made on Strepto- myces large circular and linear plasmids. In contrast to bacterial theta-type plasmids, Strepto- myces theta-type plasmids reveal diversity and novelty on the structures of replication origins, functions of replication and regulation proteins. The newly identified replication origins of linear plasmids show that it can also be located near one telomere, and two or more functional origins are observed in one molecule. The newly sequenced telomeres indicate that formation of sec- ondary structure rather than ＂folding-back＂ is important for telomere replication. Sequences of Streptomyces circular and linear plasmids imply their close relationship. Sequencing results also show that co-integration of circular plasmid and phage, and experiments demonstrate their inter-conversion under certain conditions. These results indicate that diversity, novelty and evolutionary relationship of Streptomyces circular and linear plasmids and phages.