植物乳杆菌KLDS1.0728质粒p141的分子分析

Molecular Analysis of p141 Isolated from Lactobacillus plantarum KLDS1.0728

对分离自植物乳杆菌KLDS1.0728的质粒p141进行了全序列测定,结果显示,该质粒全长为3597bp,平均G+Cmol%值为38%,并利用DNAMAN6.0软件得到该质粒限制性内切酶图谱。经NCBI网站ORFFinder软件分析确定其编码序列即ORF为15个,通过与公共数据库比对,发现可以识别功能的ORF有2个,其中包括质粒复制所必需的rep基因,p141的rep基因与已知序列的植物乳杆菌WCFS1内源质粒pWCFS101以及植物乳杆菌内源质粒pM4的复制蛋白基因相似性高达91%。根据rep基因的相似性比较,判断p141的复制模式归属于RCR模式的GroupIII组,即pC194家族。另外,还发现质粒p141中存在mob基因,表明该质粒具有水平转移能力。但没有发现Tn4430转座子以及转座酶基因topl和topA,所以可以判断该质粒的基因比较稳定。此外,还发现该质粒序列中存在一定的与质粒复制和转移调控以及蛋白质表达等有关的重复序列,其对调控质粒的拷贝数有一定意义。

A plasmid from Lactobacillus plantarum KLDS1.0728, designated as p141, was sequenced and characterized. It consisted of a 3597 bp circular molecule with a G ＋ C content of 38%. The enzyme digestion map of plasmid p 141 was obtained by the software DNAMAN 6.0. The plasmid p 141 was predicted to contain 15 ORFs by ORF Finder software in NCBI. Using the blast softvare to compare and search the genes, we found two known ORFs in the plasmid p141. Among those, rep gene was most important for plasmid replication ability. Identity analysis indicated that rep gene of p 141 was similar to that of Lactobacillus plantarum WCFS1 plasmid pWCFS101 and Lactobacillus plantarum plasmid pM4. Based on the sequence similarities among minimal replicon modules, p141 belonged to Group III family in the RCR plasmid. In addition, mob gene was existed in p141, so this plasmid had level transfer ability. But Tn4430 transposon and transposase gene topl, topA were not found in p141, and this indicated that genes of the plasmid p141 were stable. There were direct and invert repeats in this plasmid. These repeats had certain association with plasmid replication and transfer regulation, protein expression, also had significance on the regulation ofplasmid copy number.