Cox Katherine E L, Schildbach Joel F
Department of Biology, Johns Hopkins University, 3400 N. Charles St. Baltimore, MD 21218, USA.
Plasmid. 2017 May;91:53-60. doi: 10.1016/j.plasmid.2017.03.007. Epub 2017 Mar 28.
The R1 antibiotic resistance plasmid, originally discovered in a clinical Salmonella isolate in London, 1963, has served for decades as a key model for understanding conjugative plasmids. Despite its scientific importance, a complete sequence of this plasmid has never been reported. We present the complete genome sequence of R1 along with a brief review of the current knowledge concerning its various genetic systems and a comparison to the F and R100 plasmids. R1 is 97,566 nucleotides long and contains 120 genes. The plasmid consists of a backbone largely similar to that of F and R100, a Tn21-like transposon that is nearly identical to that of R100, and a unique 9-kb sequence that bears some resemblance to sequences found in certain Klebsiella oxytoca strains. These three regions of R1 are separated by copies of the insertion sequence IS1. Overall, the structure of R1 and comparison to F and R100 suggest a fairly stable shared conjugative plasmid backbone into which a variety of mobile elements have inserted to form an "accessory" genome, containing multiple antibiotic resistance genes, transposons, remnants of phage genes, and genes whose functions remain unknown.
R1抗生素抗性质粒最初于1963年在伦敦的一株临床沙门氏菌分离株中发现，几十年来一直是理解接合质粒的关键模型。尽管其具有科学重要性，但该质粒的完整序列从未被报道过。我们展示了R1的完整基因组序列，并简要回顾了关于其各种遗传系统的现有知识，以及与F质粒和R100质粒的比较。R1长97,566个核苷酸，包含120个基因。该质粒由一个与F质粒和R100质粒基本相似的主干、一个与R100几乎相同的Tn21样转座子，以及一个与某些产酸克雷伯菌菌株中发现的序列有一些相似之处的独特9 kb序列组成。R1的这三个区域由插入序列IS1的拷贝隔开。总体而言，R1的结构以及与F质粒和R100质粒相比较表明，存在一个相当稳定的共享接合质粒主干，各种移动元件插入其中形成一个“附属”基因组，该基因组包含多个抗生素抗性基因、转座子、噬菌体基因残余以及功能未知的基因。
